Forum http://www.weirdwarp.com/forum/blog-posts Simple:Press Forum Version 4.0.3 chris Dann on Actual and Artist Images of Exoplanets http://www.weirdwarp.com/forum/blog-posts/actual-and-artist-images-of-exoplanets/#p121 Blog Posts http://www.weirdwarp.com/forum/blog-posts/actual-and-artist-images-of-exoplanets/#p121 Extrasolar planets or for short exoplanets have been found in orbit around many different star systems other than ours. Exoplanets are being found all the time but take a look at this database of exoplanets for an idea on their characteristics. An actual image has been shot sometime back of an exoplanet but as you can see you might as well be looking at a pixel on a TV screen or computer which is not that exciting. When thinking about exoplanets artists minds have gone wild and lots of pictures of imaginary exoplanets have been created to fill this imaginary void. [caption id="attachment_2966" align="aligncenter" width="560" caption="A Real Image of an Exoplanet"]A Real Image of an Exoplanet[/caption] The image was taken by the Hubble space telescope by blocking out the stars light so that the exoplanet could be seen. The star is Formalhaut which is easily visible to the unaided eye. The exoplanet is called Formalhaut b. Not a fantastic name but it means it is a planet around the star Formalhaut the b meaning that it is the planet closest to the Sun. This system letters the planets from the inner to the outer but letter a is not used. The image below has been directly taken of two planets (labelled B and C) orbiting the star HR8799 by the Gemini North eight meter telescope. You can see from the picture that the Starlight has been blocked allowing us to see the two white dots which are the planets. The star is about 130 ly away but is very bright. The planets are orbiting the star at 3.6 billion miles and 6.3 billion miles respectively. A third planet was found later on but is not shown in the image. This is the first planetary system to be directly imaged. [caption id="attachment_2967" align="aligncenter" width="560" caption="Actual Image of the Star HR 8799 and Its Two Planets"]Actual Image of the Star HR 8799 and Its Two Planets[/caption] Here are some artist renderings of the star GJ876 (Gliese) and its outer planets which have masses of 2.5 and 0.8 that of Jupiter. Don't forget that one Jupiter mass is about 318 Earth masses and therefore these are huge planets. The inner planet which is a little like ours but a lot bigger is thought to have a mass about 7.5 Earth masses. In the exoplanet scientific circles it is called a super Earth and may well contain life. [caption id="attachment_2969" align="aligncenter" width="560" caption="GJ 876 's Earth like Planet"]GJ 876 's Earth like Planet[/caption] An artist rendering of a close-up of the Earth like planet around GJ876. [caption id="attachment_2970" align="aligncenter" width="560" caption="Close-Up of the Earth like Planet around GJ 876"]Close-Up of the Earth like Planet around GJ 876[/caption] Could we be in orbit around GJ876's earthlike planet one-day? [caption id="attachment_2971" align="aligncenter" width="560" caption="GJ 876 's Earth like Planet"]GJ 876 's Earth like Planet[/caption] Here’s a fly through of the Gliese planetary system. It's a little old but gives an idea of what the system is probably like.
lots of Jupiter like planets have been found around other stars. They have been given the nickname hot Jupiter's because they orbit so close to their parent star. These were the most likely type of planets to be found as they are so huge. It is thought that these planets may have migrated from the outer part of their planetary system eventually forming a very tight orbit with its star. [caption id="attachment_2972" align="aligncenter" width="560" caption="A Hot Jupiter Exoplanet"]A Hot Jupiter Exoplanet[/caption] One day we will not need artist renderings as a probe will transmit actual images back to us but hopefully by a method that doesn't take thousands of years! ]]> Tue, 24 Aug 2010 05:18:06 +0000 chris Dann on Is Human Colonisation of Europa Possible? http://www.weirdwarp.com/forum/blog-posts/is-human-colonisation-of-europa-possible/#p120 Blog Posts http://www.weirdwarp.com/forum/blog-posts/is-human-colonisation-of-europa-possible/#p120 Europa is a fascinating place. Once it was believed that Jupiter's moons were just lumps of ice and rock. But missions to Jupiter showed us that there is more to Jupiter's moons than we thought.

This moon has become much more interesting the more it is explored. The furthest we have got nowadays is to have a very good guess that there is an ocean below about 100 km of ice. Future missions are in the balance and one was scrapped due to NASA's change in direction towards commercialism of space which will in the future make much more sense than the present program but unfortunately will delay things a little.

[caption id="attachment_2909" align="aligncenter" width="560" caption="Europa with Jupiter in the Background"]Europa with Jupiter in the Background[/caption]

Let's take a jump into the future beyond the exploration of unmanned probes to Europa and think what it would be like to actually colonise this moon. The Artemis society which is home of the Artemis project has plans to colonise the moon. This is obviously an advanced idea but an interesting idea nevertheless. This thinking has extended to Europa as it looks very much like a good place to settle if the problems can be overcome. The colonisation plan covers almost everything including how to build communities in air pockets to what would be the best films to be sent (obviously 2001 a space Odyssey and the follow-ups).

There are a few sceptics to this plan and this plan is well ahead of its time but in the future things like this will occur but who knows how long into the future we will have to wait? The main problem is the radiation as a human would only be able to last about 10 minutes on the surface. About 6 foot beneath the surface of the ice the ice would provide shielding from the radiation, so it would be a pretty tense time on the surface trying to drill down 6 feet quickly before your arms fell off. The Artemis Society get around this problem by assuming that technology in the future will be able to provide electromagnetic shielding.

[caption id="attachment_2910" align="aligncenter" width="560" caption="A Future Colony?"]A Future Colony?[/caption]

Without bringing a massive lead shield from Earth which is completely impossible and extremely inefficient there is another way round this problem. Callisto has been proposed as a moon outside the radiation belt of Jupiter where a staging base could be built. The ice on Callisto could be mined and then shaped around the ship so that an orbit around Europa would not be instantly fatal.

That's not the only problem though as you might imagine. The temperature is low at -170°C on the surface and you would need more than a good set of thermals to overcome this unbelievably cold obstacle. This may not be as bad as it seems as the ice surface could produce a shield once drilled through. Th warm heat is due to tidal heating which is the constant pull and push of Jupiter's gravity on Europa as it orbits the massive gas giant heating up the core Hydrothermal vents are thought to exist on the seabed of the ocean, as they do on Earth.

[caption id="attachment_2912" align="aligncenter" width="560" caption="Melting through the Ice"]Melting through the Ice[/caption]

As we have noticed on Earth life doesn't need the light from the Sun for photosynthesis for survival. Organisms may live around hydrothermal vents and these may be at the bottom of the food chain for much larger oceangoing animals. This news would be excellent for mankind as a whole but for the colonists it could be a food source and a potential export rivalling Japanese sushi. Harmful microbes may exist though and cause some weird and wonderful diseases. If life exists then intelligent life could exist although this is a bit of a long shot and that could in the long run cause territorial disputes or be perhaps beneficial in some way.

The human body is quite frail when looking round for places to colonise and it doesn't do too well in low gravity environments. The larger the moon or planet the larger the gravity and therefore Europa is only big enough to produce 13.4% of Earth's gravity. Over time the muscles in the body will waste away and the skeleton will slowly deteriorate. Fluid will be redistributed around the bodies systems and the cardiovascular system will slow down which will weaken the immune system. Other less dramatic effects on the human body are loss of body mass, a stuffy nose, disturbed sleep and farting (yes, really). Ethical questions also come into play with the possibility of life on Europa. It would be a disaster to infect any life and destroy it as this may be our only contact for an extremely long time.

There is a small tenuous atmosphere around Europa consisting of a trace of oxygen. This is produced from charged particles from Jupiter breaking up the ice into its constituent hydrogen and oxygen molecules. The much lighter hydrogen molecules drift off into space but the oxygen molecules stay around Europa. This could be an advantage if the oxygen could be captured and used for life support although I expect most of the oxygen needed will be produced from the breakdown of water into hydrogen and oxygen.

[caption id="attachment_2913" align="aligncenter" width="560" caption="Europa with Jupiter in the Background"]Europa with Jupiter in the Background[/caption]

So what is the basic plan for colonisation? From the above you can see that there is a need to drill down through the ice from a small shielded (by ice) base on the surface. The colonists would drill down until they reach the ocean which could be as much as 100 km below the ice. An underground cavern would then be excavated or perhaps even found and would be an excellent place for a long-term base due to the protection from radiation and higher temperatures.

A big problem with the idea of colonising Europa is that it would just not be a money earner even with sushi exported back to Earth. Until the cost of spaceflight and cheap ways to survive in space are found this idea is on the edge of science fiction. Of course if there was positive signs of life on Europa then things would change rapidly, let's hope so.

]]> Wed, 11 Aug 2010 03:34:21 +0000 chris Dann on Where Should We Look for Alien Artefacts? http://www.weirdwarp.com/forum/blog-posts/where-should-we-look-for-alien-artefacts/#p119 Blog Posts http://www.weirdwarp.com/forum/blog-posts/where-should-we-look-for-alien-artefacts/#p119 SETI looks for signals that are sent by the electromagnetic spectrum and their are a lot of frequencies to search. If you pair this with the size of the universe you can see how SETI is really looking for a needle in a haystack. SETI is still a good idea as one needle in one haystack is all that is needed. There are other ideas one being the search for alien artefacts. Alien artefacts such as spacecraft, probes, dead aliens, abandoned bases, spanners etc would give a positive indication that ET had visited our solar system. [caption id="attachment_2885" align="aligncenter" width="371" caption="The ultimate alien artefact, the monolith from space Odyssey 2001"]The ultimate alien artefact, the monolith from space Odyssey 2001[/caption] The Earth and the moon have been around for about 4.5 billion years compared to the search for SETI since 1960 when Frank Drake did his first Seti experiment. As you can see 50 years of searching with SETI compared to 4.5 billion years gives a large possibility of an alien leaving an artefact in our solar system. So where would be the best places to look for alien artefacts? Earth is being searched all the time in our everyday lives as we go about our business and we haven't found anything we can say is an artefact. The oceans are mainly unexplored as the finding of hydrothermal vents and life thriving around them has shown. Our planet is not static but travels through the Galaxy as a spacecraft passing other stars and other stars passing us. With the discovery of exoplanets we may soon know how common oxygen containing atmospheres are. If these types of atmosphere are rare then the Earth would stand out to any alien civilisation around another star passing our position. If a rich alien did notice our planet and decide to investigate the moon would be a much better place to observe the Earth than in orbit or actually on the Earth itself. The moon's advantages include no atmospheric erosion of, geological problems or annoying apes/humans interfering with any equipment. [caption id="attachment_2891" align="aligncenter" width="560" caption="Far Side of Moon"]Far Side of Moon[/caption] The advantages the moon brings to equipment placed for Earth monitoring when compared to an object in orbit around the Earth are protection from meteorites and radiation, fuel not needed to maintain its orbit, a source of materials for repair, heat control and support for life. If they fancied hiding the moon would obviously be a much better place than advertising their presence around the Earth in orbit. The moon's much lower gravity may also be preferred. Aliens would probably look at a landing on the moon as essential just as we are looking at Phobos as a base for missions on Mars. Therefore the moon could be full of artefacts. Large artefacts over time would probably disappear due to meteorites but the smaller bits and pieces such as parts of old destroyed artefacts may still exist beneath the surface covered by dust and meteorite impacts where they would be protected from further bombardment. [caption id="attachment_2886" align="aligncenter" width="295" caption="Perhaps a Ruin like Formation on the Moon?"]Perhaps a Ruin like Formation on the Moon?[/caption] If an alien is thinking the same way as us it may well think that the moon is a likely place for alien artefacts and leave its own artefacts that we could eventually find. Unless the aliens are very green they will probably pollute the space in our solar system. This could mean that artificial alien satellites have disintegrated into debris, each piece of debris having a different chemical composition which could be shown in multicoloured bodies. There is so much junk in orbit around the Earth that it would take quite a long time to search. Much further out where our pollution hasn't affected the solar system we may have more luck. If we look for debris that has fallen to Earth it is very easy to mistake objects and make false claims as many people do without significant evidence. Most are meteorites and lots of objects are classed as UFO's but are actually objects that just have not been identified and are not spaceships etc. It would be very odd that they have flown all the way just to annoy us and fill up the Internet with lots of UFO pictures. Rubbish from an alien civilisation could leak into the interstellar medium and eventually reach us. This could be due to light pressure which could expel extremely small debris particles from such things as rocket engines. An artefacts interaction with a planet may cause it to assume an asteroid or comet like motion due to gravity and therefore be flung away from a planetary system possibly towards our solar system. Computer simulations have been carried out and about 10 to 30% of small bodies are predicted to leave the solar system. Explosions of artefacts such as satellites and spacecraft could propel artefacts away from a planetary system. [caption id="attachment_2893" align="aligncenter" width="394" caption="Crop Circles Were Good Entertainment but Turned out to Be Hoaxes"]Crop Circles Were Good Entertainment but Turned out to Be Hoaxes[/caption] Obviously these artefacts are going to take a long time to travel to us from even the closest star but don't forget that the solar system has been around for about 4.5 billion years, it just depends on when the artefacts were expelled. The search for alien artefacts may become more relevant in the future as we explore more and more of the solar system and as time goes by. The attitude towards this type of search for intelligent life signs doesn't go down that well in most scientific circles although if you look at Seti it was once called pseudoscience but has been more widely accepted today. With the invention of astrophysics and astrobiology years ago people are beginning to accept that it is worth looking for signs of alien life. If basic life is found in the solar system on, say, Europa then the search may gain momentum and finding signs of intelligent life or complex life itself may become a reality. ]]> Wed, 04 Aug 2010 04:30:14 +0000 chris Dann on Extremophiles on Other Celestial Bodies? http://www.weirdwarp.com/forum/blog-posts/extremophiles-on-other-celestial-bodies/#p118 Blog Posts http://www.weirdwarp.com/forum/blog-posts/extremophiles-on-other-celestial-bodies/#p118 Archaea and bacteria and are classified according to the environment in which they live. Just to show you how easy it would be for extremophiles to exist on other planets, moons, satellites, asteroids or comets I will run through a few types below. Temperature Loving Extremophiles. The lowest temperature for extremophiles is -18°C. The main problem with life and low temperatures is that the cold forms crystals of ice which can rupture the cells. Psycrophiles are the type of extremophiles that just love low temperatures. I am therefore by definition not a psycrophile. They grow best at 4°C and do not like temperatures above 12°C for reproduction, very fussy! As mentioned before the main problem is ice freezing their cells and they get round this by making the membrane of the cell more fluid and therefore less likely to crack and rupture. They also use soluble compounds that lower the normal freezing point of water and in the case of glycerol they can survive down to -60°C. [caption id="attachment_2868" align="aligncenter" width="560" caption="Chlamydomonas Nivalis a Psycrophile"]Chlamydomonas Nivalis a Psycrophile[/caption] Hyperthermophiles love the heat. They can reproduce at temperatures greater than 80°C living in temperatures of 100°C or even more. There are more than 50 different types of Hyperthermophiles and the most resistant found to date grows on the walls of black smokers on seafloors. These Hyperthermophiles are called pyrolobus fumarii and reproduce at 105°C but below 90°C they don't grow at all. The temperature range of extremophiles means that they could exist on comets or asteroids, on some of the planets and on some of the satellites like Europa with its outer icy surface and possibly hot interior with possible hydrothermal vents. [caption id="attachment_2869" align="aligncenter" width="570" caption="Black Smoker Hydrothermal Vent"]Black Smoker Hydrothermal Vent[/caption] Extremophiles That Can Survive Radiation The Sun can make us brown but it can also destroy DNA. We are lucky because we are protected by the atmosphere but other planets throughout the solar system don't always have this luxury. Deinococcus radiodurans an extremophile that can survive the harshest of radiation environments. It is one of the toughest extremophiles and can withstand high ultraviolet and gamma radiation. It can do this because it is an excellent rebuilder and rebuilds its DNA from fragments that had been damaged by the radiation. This ability may be due to it being ring like which keeps fragments closer together and allows them to rebuild. Radiation is a problem throughout the solar system and the other planets aren't protected as well as ours. But radiation extremophiles gives us hope that life may exist in the most irradiated of environments. [caption id="attachment_2870" align="aligncenter" width="560" caption="Deinococcus Radiodurans"]Deinococcus Radiodurans[/caption] Acidic and Alkaline Extremophiles There is a scale called the pH scale and life as we know it must live at the centre of the scale. This type of extremophiles can survive in all sorts of acidic and alkaline environments at either end of the pH scale. Acidophiles, as the name suggests, survive in acidic environments by keeping the acid out and maintaining neutrality inside their cells. This allows them to survive in geochemical environments such as hydrothermal vents and some hot springs. Alkaphiles live within alkaline environments and survive in the same way as acidophiles by maintaining a neutral environment inside the cells. These can be found in soils with carbonates and soda lakes. [caption id="attachment_2872" align="aligncenter" width="560" caption="Lake Natron, a soda lake in Tanzania"]Lake Natron, a soda lake in Tanzania[/caption] Salinity Type of Extremophiles These types of extremophiles require salt to live. We are not talking about the salt found in sea water but twice to nearly 5 times that. They are called Halophiles and can be found in the evaporation basins where the environment may also be alkaline as well. [caption id="attachment_2871" align="aligncenter" width="560" caption="Halophiles"]Halophiles[/caption] Extremophiles Subjected to Desiccation Desiccation is extreme dryness or extreme drying of the extremophile. This isn't such a good thing because all living things on earth depend on water but the extremophile anhydrobiosis can do without moisture. Anhydrobiosis goes into a state of suspended animation where there is little transfer of water in the cell and no metabolic activity. The organism therefore looks dead when it has dried up but with the application of moisture it comes back to life. This happens in bacteria, yeast, fungi and in plants and animals where water is sporadic. [caption id="attachment_2873" align="aligncenter" width="237" caption="Tardigrade Extremophile, Dubbed Waterbear, Can Survive in Space Dessicated"]Tardigrade Extremophile, Dubbed Waterbear, Can Survive in Space Dessicated[/caption] Pressure Resisting Extremophiles Piezophiles can resist under a large amount of pressure. They do this by making their membrane fluid and allowing the cells to pack together. There has been work on Piezophiles on the international space station. They have studied them in a weightless environment and are trying to work out how the weightlessness affects the cells and how they work. When looking at other celestial bodies for life we were once quite restricted as we were looking for life that could exist within human limitations. Extremophiles give us a larger range of environments that may possibly support life. It may be possible that there is intelligent life existing in the weirdest places in the harshest of environments. This draws us to the conclusion that we should not just look for life in habitats that would suit humans but should continue the search in every nook and cranny in every possible environment. ]]> Tue, 20 Jul 2010 11:07:16 +0000 chris Dann on How to Talk to Aliens http://www.weirdwarp.com/forum/blog-posts/how-to-talk-to-aliens/#p117 Blog Posts http://www.weirdwarp.com/forum/blog-posts/how-to-talk-to-aliens/#p117 Dr Hans Freudenthal in one of his books called "lincos: design of a language for cosmic intercourse, part one”. In 1999 Yvan Dutil from Canada created a message from Lincos  that he thinks may be able to be decoded and read by aliens with no knowledge of humans. [caption id="attachment_2853" align="aligncenter" width="560" caption="Lincos Explained"]Lincos Explained[/caption] Dutil is an anti-cryptographer as opposed to a cryptographer and therefore tries to make information as easy to read as possible. The four hour message was transmitted into space by a Russian radio telescope in 1999. The radio signal shifts back and forth between two frequencies which are 48 kHz apart. It is a form of binary with one frequency representing on and the other off. Put together, just like a computer does, the ons and offs can form any language that is required. [caption id="attachment_2848" align="aligncenter" width="560" caption="Radio Telescope"]Radio Telescope[/caption] The message's journey will encounter distortion by static which will make it hard to read at the other end. Redundancy is the solution. Redundancy is a way to make the message readable even if information is lost. T-e ca- jum--d is readable with a little thought and comparison of other words in the message. We compare the words to the words that we already know but the aliens would compare it to other words in the message. Patterns are also a part of the redundancy in the message one pattern being a box around each page. If one page's box is distorted comparison with other page's boxes will show how to correct the distorted page. This will allow the message inside the box to be read. Even more redundancy is included in the actual message. Each symbol is a picture which is seven bits high and five bits wide representing a single concept such as numbers, objects or ideas such as pressure (one bit = one frequency, the other bit = the other frequency). Each one of these symbols differs from the others by at least seven bits which is enough to correct any error of three bits. This means that if a 10th of the message was lost it would be possible to reconstruct the whole message. The actual message is full of patterns at regular intervals which it is hoped they would pick up. For this some sort of sight is necessary and it is assumed that they would have this sight if they had received the signal through a radio telescope. [caption id="attachment_2855" align="aligncenter" width="560" caption="Lincos Units"]Lincos Units[/caption] To learn our language they need to be taught the various symbols. This is done within the body of the message by making the beginning of a message very predictable. This is where lincos comes in which is a jumble of mathematical symbols. All our assumptions about maths and language are put to one side and lincos build them up from scratch. Every symbol is defined by symbols that come before and this means that the first symbols must be concepts that have no definition. Maths is the best language to send as nations on earth in the early days learnt how to count but weren't communicating with each other. This would imply that aliens would be able to read the mathematical message. The first line of the message that Dutil sent contains numbers from zero upwards. Each number is transmitted in three different ways as dots, as a binary number and larstly as a strange looking numeral. The second page lists prime numbers and the third teaches them how to add up. Edition is followed by subtraction, multiplication, division and exponentiation. The section ends with good old Pi which can be found in a lot of places in mathematics and the Pythagorean theory (remember triangles!). These are some of the oldest mathematical objects that were made by human beings. [caption id="attachment_2847" align="aligncenter" width="343" caption="Lincos Language"]Lincos Language[/caption] Then the message moves on to chemistry and physics including time and distance, mass and charge and temperature amongst others. From these basic concepts sounds, solar systems the Earth and humans are described. DNA and the radio telescope's properties come close to the end with the message finally finishing with a request from the aliens for the same information back, let us hope they are not freeloaders! Nothing has been heard yet (unless it was filtered into the spam box) and we are still waiting. If this message worked we should receive a message at any time but let's hope we recognise the message back. ]]> Tue, 13 Jul 2010 05:49:32 +0000 chris Dann on All about Meteorites http://www.weirdwarp.com/forum/blog-posts/all-about-meteorites/#p115 Blog Posts http://www.weirdwarp.com/forum/blog-posts/all-about-meteorites/#p115
  • A meteoroid is an object moving in interplanetary space smaller than an asteroid but larger than an atom, this can obviously include dust or ice from a comet or other fragments or dust.
  • A meteor is a Meteoroid that has entered the Earth's atmosphere and is producing a streak of light as it burns up.
  • A meteorite is a meteor that has actually struck the ground.
    • There are things called meteor showers that I've talked about before in recent posts and these are just a lot of meteors falling to Earth giving us a light show. You will have the image, when talking about meteors, of a ball of fire streaking to Earth and then creating havoc destroying towns and cities. That is not so when you get further into the subject of meteors. Meteors can be very, very small and are then called Micrometeors. [caption id="attachment_2584" align="aligncenter" width="560" caption="Fireball"]Fireball[/caption] These can be as small as atoms and dust and drift down over months to the surface of the Earth. If you are standing outside for a few hours you will probably be hit by one of these particles. It didn't hurt though did it? That's because the smallest atoms or particles get slowed down by the frictional drag of the atmosphere and lose the velocity they had in interplanetary space. Meteorites come from all over the solar system bringing us all sorts of information from their makeup. Scientists classify the meteorites into three types depending on what they are made of-
    • Iron meteorites which are mostly made of iron. These make up around about 5% of all meteorites and are between 10 to 40 kg.
    • Stony meteorites which are made up of silicate minerals. These make up around about 94% of all meteorites and are about 1 to 10 kg.
    • Stony-iron meteorites are a mixture of both and are made up of metals and silicates. These make up the remaining 1% of meteorites that are found on the surface of the Earth.
    Meteorites have become very precious because of their rarity and scientists have a hard time finding original samples. They use a network of trusted people to get samples to test. Because of this and because the Earth is covered in all sorts of rocks and metals there are not so many meteorites found as actually fall to the Earth. One of the best ways of finding samples is to actually see a meteor hit the ground and then go to the impact site. When a meteorite has been seen to fall to earth it is called a meteorite fall and the best finds have been found in this way. When a meteorite has been found and was not seen to fall to earth as a meteor it is called a meteorite find. Large meteorites are mostly found with meteorite finds the largest being Hoba. [caption id="attachment_2582" align="aligncenter" width="560" caption="Hoba"]Hoba[/caption] So once meteors have hit the ground creating meteorites what information can they give us? The most interesting information comes from things called chondrites. About 86% of the meteorites that fall on Earth contain these small round particles. They are mostly made up from silicate minerals that have been melted while they were floating around in space. They are very old and date back from the origins of the solar system. [caption id="attachment_2583" align="aligncenter" width="560" caption="Chondrite"]Chondrite[/caption] They are thought to have escaped the collisions which created the planets and to contain the building blocks of the solar system. Knowing what the building blocks of the solar system were gives us a good picture of how the solar system was created and the composition of different planets other than Earth. Achondrites are meteorites that do not contain chondrites. They are useful though as they contain rocks that are similar to igneous rocks. They are thought to contain the crustal material of asteroids and some of these chondrites have been brought back from the moon. As you can see meteorites give us a picture of how the solar system was formed although we could still do with rocks from all the different planets. Unfortunately though, this is probably the best we will get for some time. If you'd like a free poster to download about Canadian meteorites then try this poster. While you are clicking links you might as well try this in database from the Natural History Museum and find out how many meteorites have hit your country. Just in case you aren't asleep yet here's a very good site on meteorites. ]]>     Mon, 10 May 2010 06:26:48 +0000     chris Dann on Interplanetary Dust Our Minute Friend http://www.weirdwarp.com/forum/blog-posts/interplanetary-dust-our-minute-friend/#p114 Blog Posts http://www.weirdwarp.com/forum/blog-posts/interplanetary-dust-our-minute-friend/#p114 It is black out there, very black. In between the specks of light called stars and in between the galaxies there is just a lot of black. That may be true to our eyes but it is not true at all. In the darkness of space in the black bits there is a giant monster called dust.
    Okay, okay dust isn't a monster but it got your attention didn't it? You probably think that dust is a boring subject but it is far from that if you take the time to look closely at it (very closely as dust tends to be quite small). Calling the particles dust gives the wrong impression in some respects and the right impression in others. Dust particles are the very basis of our solar system as it may have been a cloud of dust that produced the Sun and eventually the planets.
    [caption id="attachment_2514" align="aligncenter" width="582" caption="interplanetary dust"]interplanetary dust[/caption] Dust particles are mostly less than 1 mm in diameter. They are a mixture of many elements and compounds but the most abundant being silicates and glassy nodules with perhaps a few sulphides, metals and other minerals and carbonaceous material. They were once a curse to astronomers as large clumps of gas tended to get in the way when they were scouring the sky for things that astronomers tend to scour the sky for. Dust particles were discovered by observing the zodiacal light that appears in the night sky extending up from the vicinity of the Sun. This light is produced by the dust particles scattering and reflecting the sun's light and causing a faint glow. This was a big clue as to the existence of interplanetary dust. [caption id="attachment_2515" align="aligncenter" width="500" caption="zodiacal light"]zodiacal light[/caption] There are three main sources of interplanetary dust these being cometary emissions, particles from asteroids and dust particles from impacts around the solar system mainly in the Kuiper belt and asteroid belt. The asteroid belt lies between Mars and Jupiter and the Kuiper belt lies just beyond Neptune which is a source for comets. Another source for comets but much, much further out is the Oort cloud. Most of the comets in the Kuiper belt have short orbital periods (time taken for one complete revolution around its orbit) and so their effect is much more than the orbits of comets from the Oort cloud which are thought to take tens of thousands of years but obviously are quite hard to measure! Comets are quite important to us not only because they could impact the Earth but because they leave a trail of particles. A comet is made up of mostly dirty, icy rubble that tends to break off and leave a trail of dust behind it. The trail of debris follows the orbit of the comet and forms a tube of dust particles which is called a meteoroid stream. All active comets produce a meteoroid stream and I expect you can imagine that when the Earth passes through a meteoroid stream the meteoroid stream will have an effect on the Earth. As the meteoroids enter into the atmosphere the atoms of the meteoroids get excited and heat up. A byproduct of this is the production of light and this produces a streak of light. This effect is probably most well known as a meteorite shower and some spectacular effects can be seen if you're in the right place at the right time. 50 meteor showers occur every year. If you fancy your luck in catching a meteorite shower (well worth the effort) then try these viewing tips. If you just can't be bothered and fancy the easy option then take a look at the video below. [caption id="attachment_2517" align="aligncenter" width="488" caption="comet"]comet[/caption] Dust particles aren't just in the wake of comets but crop up all over the solar system. This is because of three processes, orbital evolution, the Poynting-Robison effect and radiation pressure. Orbital evolution isn't just restricted to dust particles but also to any other body in the solar system. This is the effect of the gravity of the planets, especially the giant planets such as Jupiter and Saturn, on the orbits of the dust particles. It's quite simple really, if the particle gets too close it gets pushed around. Radiation pressure is the force that light exerts on the particle. Light is made up of photons and these have momentum. When they hit the particle they transfer momentum to the particle and give it a little shove. This may not sound plausible but when you think of how small the particle is it shouldn't be such a shock. This force over quite a bit of time can push the particle out of the solar system. the Poynting-Robison effect is related radiation pressure. It has an almost opposite effect as radiation pressure does. Each particle has a slight motion and 90° away from its main path and this means that the photon can come from the side (extremely and very slightly). This has the effect of slowing down the particle in its orbit and after many orbits the particle slowly spirals in to the inner solar system. Very large particles are affected by this but most effect is seen on the very small particles and a 10 Micro metre size particle can take 10,000 years to reach the inner solar system which is not that long really when you think that the solar system is a 4.56 billion years old. Particles as mentioned before are the building blocks of the solar system and the universe and can give us quite a light display on certain nights. Hopefully after learning a bit about dust particles you will never think of dust in the same way again or perhaps you will? Here's a podcast on planetary dust made by astronomy cast and the lazy way of seeing shooting stars. [podcast]http://www.weirdwarp.com/wp-content/uploads/2010/04/planetary dust podcast.mp3[/podcast]
    ]]>     Tue, 20 Apr 2010 05:14:35 +0000     chris Dann on Big and Small Asteroids and Their Formation http://www.weirdwarp.com/forum/blog-posts/big-and-small-asteroids-and-their-formation/#p113 Blog Posts http://www.weirdwarp.com/forum/blog-posts/big-and-small-asteroids-and-their-formation/#p113 [/caption] Unfortunately these asteroids don't stay in the orbit between Mars and Jupiter but can cause us some hassle. Collisions between asteroids in the asteroid belt and the complex interactions of gravity of the planets and asteroids can cause an asteroid to come out of the asteroid belt and fly in a different trajectory. When these asteroids get closer to Earth they are called near Earth objects (NEO) which also includes comets and any other pieces of space junk that can be a danger to Earth.a These rogue asteroids mostly tend to avoid hitting the planets causing impact craters and,  mass extinctions, poor old dinosaurs. There are many more smaller asteroids than larger ones, the largest being Ceres with a diameter of 913 km, pretty big! Ceres was called a dwarf planet that was lowered in status to an asteroid some time ago. It is in the asteroid belt and contains almost a third of the belts total mass. Recently it has been seen to be spherical unlike the other asteroids around it which are an irregular in shape. If you were to land on a Ceres you would probably find a mixture of water ice and various hydrated minerals such as clay. It is also thought to have a Rocky core and icy mantle beneath this mantle could be water and all the hope for life that that gives. No space probes have been to Ceres but there is a mission that is on the way at the moment. This is the dawn mission which should reach Ceres in 2015 after passing by the asteroid 4 Vesta in 2011. It will enter orbit around Ceres at about 6000 km and then reduce its orbital distance to about 700 km taking about 12 months to do this. This is called the Dawn Mission and it will be quite an interesting time when it starts to send back information. Asteroid can be classified into various types so that scientists who enjoy looking at rocks can chat about them. C-type- carbonaceous types, dark (reflective), primitive S-type- Stony or Stony metallic, more reflective, more red, fragments E-type- highly reflective, enstatite (magnesium silicate MgSiO3), fragments D-type- (dark type) dark, red, primitive M-type- (metallic type), mostly iron and nickel, fragments P-type- (pseudo M type), metallic component These are only a few types of the classified asteroids and are not the only way to classify them either. A primitive asteroid is one where collisions have not changed the composition or surface features much. These are quite useful asteroids and some have been found on Earth giving us indications of what was around at the time of the formation of the solar system. Astronomers have noticed, while spending sleepless nights looking through their telescopes, that different classes of asteroid occupy different parts of the asteroid belt. This is because of the distance from the Sun. Obviously if you get closer to the Sun it is hotter and further away it is cooler and this means that elements that melt at lower temperature are not found further away from the Sun but only the elements that can survive the heat of the sun are found. [caption id="attachment_2498" align="aligncenter" width="530" caption="Bone shaped asteroid"]Bone shaped asteroid[/caption] Asteroids aren't just balls of rock that are perfectly spherical. Some asteroids are called binary asteroids and orbit each other they are much more common than previously thought. It is quite easy to see the larger asteroids but what about the smaller asteroids? There are a few techniques that are used to work out what shape an asteroid is and are used independently or together. Obviously a spacecraft flyby is first on the list but to have a probe passing by every single asteroid would be just a little bit uneconomical. Radio transmitters used together with telescope dishes like the one in Arecibo give some very detailed information and then there is radar techniques as well that can be used to image the asteroid. It has been found that most asteroids are rubble fragments bound together by their own gravity. This means that between the rubble fragments there are cavities. C-type asteroids for instance may be 80% porous. [caption id="attachment_2496" align="aligncenter" width="500" caption="landing site of NEAR on Eros"]landing site of NEAR on Eros[/caption] There has actually been a landing an asteroid. The Eros asteroid was approached by the NEAR spacecraft. Eros was the first near Earth asteroid that was discovered. The NEAR  spacecraft was sent to intercept Eros and orbited it which was a fine feat in itself but at the end of the mission it was decided to try and make a landing on the asteroid. This was carried out and some great pictures were returned. [caption id="attachment_2494" align="aligncenter" width="531" caption="Images of landing on Eros"]Images of landing on Eros[/caption] Asteroids can be larger pieces of rock that are totally boring but on the other hand they can be very interesting libraries of information of the early solar system. One day of course we will be mining the asteroids for minerals, rock and perhaps water as well for use as a propellant. They can also be used for living on as most of them are porous and have caves and their services will protect the inhabitants from radiation. For now though we are looking and you can look to as the pictures and information from the asteroids and solar system flood in. Go take a look! ]]> Mon, 12 Apr 2010 12:21:03 +0000 chris Dann on Atmosphere's of the Gas Giants http://www.weirdwarp.com/forum/blog-posts/atmospheres-of-the-gas-giants/#p112 Blog Posts http://www.weirdwarp.com/forum/blog-posts/atmospheres-of-the-gas-giants/#p112 [/caption] We don't have a lot of information about the gas giants as the further they are away from the Sun The Harder They are to get to and retrieve information. There is also the problem that anything that enters the atmosphere will get crushed. Voyager and Galileo gave us a lot of information about Jupiter and Cassini is sending back information on Saturn At the moment. So how can we work out what is inside an inaccessible gas giant? Sneaky scientists tend to use what they can see such as the degree of flattening of the planet, the changes in gravity and measurements of the magnetic fields. None of the planets are perfect spheres And Jupiter is no exception. This flattening affects gravity and And gives a few clues as to what lies below. Another way gravity can be used is to measure it and use this to work out the composition. [caption id="attachment_2486" align="aligncenter" width="502" caption="Saturn"]Saturn[/caption] Density of Jupiter and Saturn is very low and the mass of material in these planets large Therefore the interior must be at a very high pressure. At the very edge of the atmosphere The pressure is the same as that on Earth but at the centre it is estimated that the pressure is 50 million times that of Earth. Because of this overall low-density Saturn and Jupiter must be made out of hydrogen and helium. Another indication that this is probably true is that the original elements that made up the solar system had a very high proportion of hydrogen and then, coming second in abundance, was helium. The other part of Jupiter is hydrogen and helium and this then turns into helium and metallic hydrogen under the extreme pressures. This is quite a big layer and then we reach a small icy Layer and then getting to the core a Rocky/icy material. There are Clouds on Jupiter With the topmost cloud layer consisting of ammonia. Ammonia is that smelly smell that takes no prisoners. The next layer down is a cloud of ammonium hydro-sulphide and then below this a good old layer of water vapour clouds. It is not a very pleasant atmosphere with high-speed winds and turbulence. The most interesting storm that we can see is the great red spot. Observations have shown that this has been around for 470 years and might be there for a good time yet, around about 300 years. The spot rotates about every six days and rotates anticlockwise, a poor little earth could fit into it! Close to the red spot are three white vortices. These were observed by the Voyager and Galileo spacecraft. In between the time of observation between Voyager and Galileo the white vortices drifted eastwards and closer together. These white clouds are about 1000 km across and extend down to the water cloud layer. The great red spot gives us a few clues as to what is going on lower down in the atmosphere but also raises a few as well. One of the main question is the obvious one of why it is such a lonely spot and why there isn't another spot in the other hemisphere. The colours of the spot don't really add up to the picture we have of the general atmosphere as it descends lower and changes colour. The atmospheres of Saturn and Jupiter are roughly the same except Saturn has much higher winds than Jupiter. Uranus and Neptune are much further out but are similar to each other. The densities of these two planets tell us that they have a higher ratio of the heavier elements compared to hydrogen and helium. Therefore they both have a hydrogen and helium outer layer which is smaller than Jupiter and Saturn's and then a big icy layer with about the same size Rocky/icy core. Uranus doesn't have much of a cloud system and what it does have is methane clouds lower down. Neptune has the same methane clouds that Uranus has and also a few ethane and similar clouds. Information on the giant planets atmospheres and composition are very scarce and some good results have been found using evidence from ground-based telescopes and the Hubble space telescope. As time goes by more information will probably prove the above wrong or right. As the case may be it is a good idea to have a general idea of what is going on in these type of planets anyway just in case you fancy a visit. ]]> Mon, 05 Apr 2010 13:08:36 +0000 chris Dann on How to Measure the Atmosphere of Another Planet http://www.weirdwarp.com/forum/blog-posts/how-to-measure-the-atmosphere-of-another-planet/#p111 Blog Posts http://www.weirdwarp.com/forum/blog-posts/how-to-measure-the-atmosphere-of-another-planet/#p111 [/caption] Gas chromatography works by pumping a gas (a planet's atmosphere) along a tube that is filled with packing and coated with a liquid. The soluble liquids dissolve and are released later by applying a gas. The soluble gases that are slowed down take longer to come out from the end of the tube than the insoluble ones. This means that each gas will come out of the tube at a different time. To identify which gas is which the gas chromatography instrument must be calibrated with authentic samples so that we can tell what each test is when it comes out of the tube. [caption id="attachment_2469" align="aligncenter" width="396" caption="Viking Lander"]Viking Lander[/caption] NASA had a program called the Viking program to probe Mars, Viking 1 and Viking 2. There were two components to the spacecraft one part would orbit Mars and the other landed on Mars. The one that landed on Mars carried out gas chromatography just on the atmosphere but on the surface as well. They didn't find much but the information they did find was what they had until the 1990s. As mentioned before the output of the gas chromatograph had to be identified and this was identified by a mass spectrometer. This is called gas chromatography-mass spectrometry and can only be used if a sample is introduced into the instrument (yes, it is just one instrument). It is probably a good idea to say here that spectrometry is the same as spectroscopy which is the same as spectrography. There are a few differences but they are very, very small differences. Mass spectrometry which I mentioned has been used on the Viking missions and is the way that the gases are recognised from the output of the gas chromatography instrument. There is another way though! Infrared spectroscopy measures the light or other electromagnetic radiation given off or absorbed by the gas. Because the light and the electromagnetic spectrum are used telescopes and spacecraft can find out the makeup of an atmosphere from a distance. This is looking more useful isn't it? There are a lot of different types of spectroscopy measuring different parts of the spectrum. This includes the visible, infrared, ultraviolet and x-ray. If you want to see all the different types then try this article spectroscopy. Infrared spectroscopy is particularly useful. It is used for a variety of things such as forensic science but we are more interested in using it to find out what is in the atmospheres of planets at great distances. When a beam of light is passed through a prism it is possible to see the visible spectrum and if the beam came from a thermal source the beam would contain all visible wavelengths and the prism would show a multicoloured band. There are two ways of identifying the output of the spectrometer. If you look at the absorption spectrum then you will see dark lines where the molecules of gas have absorbed the light and not interfered with the other light that has not hit any molecules. The other way of identifying gas molecules is to look at the emission spectrum which is the light given off by the gas itself. [caption id="attachment_2472" align="aligncenter" width="465" caption="Infrared Spectrometer on Cassini"]Infrared Spectrometer on Cassini[/caption] For an example of a spectrometer on a spacecraft then the ion and neutral mass spectrometer (INMS) on the Cassini is a good example. It is collecting data to identify the components of Titan's atmosphere and the magnetosphere of Saturn. It is also having a look at Saturn's icy rings and moons. Infrared spectroscopy is used by the wise (widefield Infrared survey Explorer) telescope. That's a pretty good name for something that is giving fantastic images. Wise is looking at asteroids, cool stars and the most luminous galaxies. Wise is giving some great images such as this one of Comet sliding spring. [caption id="attachment_2471" align="aligncenter" width="490" caption="WISE Infrared View of Comet Siding Spring"]WISE Infrared View of Comet Siding Spring[/caption] When it comes to much further off planets it looks like spectroscopy will be a very good indicator of whether life exists. The more advanced spectrometers get the more information they will give and the better the results so it will be only a matter of time until there is a very similar planet to Earth mentioned in the news. ]]> Mon, 29 Mar 2010 11:17:16 +0000 chris Dann on Atmospheres of the Earth and terrestrial planets. http://www.weirdwarp.com/forum/blog-posts/atmospheres-of-the-earth-and-terrestrial-planets/#p110 Blog Posts http://www.weirdwarp.com/forum/blog-posts/atmospheres-of-the-earth-and-terrestrial-planets/#p110 [/caption] The atmosphere is reasonably heavy at 5,000,000,000,000,000,000 kilograms and becomes thinner with increasing altitude with no real boundary between itself and space although 75 miles is where spacecraft start to feel the effects of the atmosphere as their heat shields start to work and they get buffeted around. There are a few questions you might ask yourself about the atmosphere of the Earth and of other planets and moons. Where did it all come from is a good start? As you might expect some of the atmosphere was formed from the original creation of the solar system. When the sun had formed a solar nebula formed around it (a swirling disc of dust and gas) and some others remained as gas and formed around the rocky bodies. The planets themselves give off gas from all sorts of sources from within the planet. The solar wind may have given us part of the atmosphere as well. The solar wind is a stream of charged particles from the atmosphere of the Sun consisting of electrons and protons. They escape the Sun because they are moving fast and they actually have a higher temperature than the core of the Sun. This is solar wind nowadays is lethal to us but we have the protection of the magnetosphere which is like a force field protecting us. In the early days of formation of the Earth may have been that this force field was non-existent and the particles from the solar wind were caught by the Earth as part of the atmosphere. There is one thing that is important for planets and moons to enable to keep an atmosphere. The gravity is the mysterious force that keeps the molecules of the atmosphere from escaping in to space although a small amount of molecules escape into space all the time. The gases of the atmosphere actually have mass and therefore gravity can act on them and just like us gravity keeps them tied to the Earth (although, they are not as heavy and therefore find equilibrium between gravity’s pull and wanting to escape and therefore remain suspended in the air). Well, that's enough about the Earth what about the other planets and moons. Do they have atmospheres? Mercury Mercury is a poor soul being so close to the Sun and being hammered by the solar wind. The atmosphere really only has trace elements in very small quantities. Being small Mercury has a lack of gravity and lost its hold over any atmosphere that may have been around. Venus Venus has a similar size to Earth and is a reasonable distance from the Sun so it should have atmosphere like the Earth's right? Unfortunately that isn't the case. The atmosphere is much denser and hotter than that of Earth. In fact it has a pressure that is 90 times that of Earth. [caption id="attachment_2454" align="aligncenter" width="336" caption="Venus Atmosphere Greenhouse Effect"]Venus Atmosphere Greenhouse Effect[/caption] Venus has lost the bubble really. The carbon dioxide which takes up almost 100% of the atmosphere has built up to such a level that it keeps the heat from the sun from escaping. You would think that with a cloud level such as Venus has (100% coverage) that no more radiation from the sun would reach the surface of the planet and the greenhouse effect would disappear. Unfortunately the sun's rays still penetrate through the clouds and fuel the greenhouse effect. This is down to what scientists call the Goldilocks theory. Before you all go to sleep this is very simple. What it boils down to is that planet must be in exactly the right distance from the Sun for the correct conditions to create an Earth like planet. The porridge must be just right! Venus is just too close and didn't win the solar nebula lottery. Mars Going back to Goldilocks, Mars is just too far from the Sun and is cold. Mars has a thin atmosphere and has a low atmospheric pressure. It consists of 95% carbon dioxide, 3% nitrogen and 1.6% argon. There has recently been found traces of methane which is quite encouraging when thinking about the possibility of life. [caption id="attachment_2455" align="aligncenter" width="502" caption="Mars Atmosphere"]Mars Atmosphere[/caption] Mars does have clouds but there is only a small percentage that is made of water vapour and of carbon dioxide. The main clouds are dust which for about once a year can cover the whole surface. When compared to Earth there are some very odd atmospheric movements on Mars. Condensation flow occurs when the face of Mars facing the Sun heats up and causes the polar carbon dioxide icecap to evaporate and rise flowing in the upper atmosphere to the southern pole. The South Pole (because it is in its winter phase) cools and carbon dioxide solidifies from the atmosphere increasing the size of the southern polar ice cap. Titan Is a moon circling Saturn and has given scientists quite a surprise. It has a thick atmosphere and is the only object other than the Earth for which evidence of a liquid has been found. The atmosphere is 98.4% nitrogen with the rest being 1.6% methane and other gases. Being so far away from the Sun and well out of the Goldilocks zone it shouldn't really have an atmosphere. Titan has managed to break the rules by keeping its atmosphere cool and I mean really cool which makes it heavier and keeps it from escaping. Titan has methane rain that has produced lakes and rivers. Because of the low gravity when it rains the drops are large and would float down to the surface like snow. I have covered the terrestrial planets in this post but don't worry I will cover the gas giants and other planets, the outer planets, in a Future post. An atmosphere is essential to us although it may not be essential to some other life form living elsewhere. Everybody has heard of climate change and it may be a very good idea to keep our atmosphere in tip top condition considering we breathe it, well at least until we find another suitable planet and have built spaceships that can get there in a reasonable time. The solar system is not the only place that has atmospheres around planets- ]]> Mon, 22 Mar 2010 14:04:11 +0000 chris Dann on The Different Types of Impact Craters and How to Spot Them. http://www.weirdwarp.com/forum/blog-posts/the-different-types-of-impact-craters-and-how-to-spot-them/#p109 Blog Posts http://www.weirdwarp.com/forum/blog-posts/the-different-types-of-impact-craters-and-how-to-spot-them/#p109 The way those intelligent scientists classify craters depends on-
  • The size of the thing hitting the surface.
  • The speed of the thing (I'll call that impactor to sound intelligent).
  • The things that the impactor are made up of.
  • The composition of the rock that is being impacted (the target rock).
  • The angle that the impactor hits the surface.
  • The gravity of the target planet.
  • How porous or strong the impactor is.
    • Microcraters Working from the smallest to the largest, microcraters can be as small as no 0.0000001 metres in diameter. These are made by hypervelocity (over 3000 m/s and allows metals to behave like a liquid).
    Simple craters
    Simple craters are next up on the scale and are a bit more of a serious beast. Meteor crater in Arizona is a typical example of a simple crater. A simple crater is up to several kilometres in diameter and has no central uplift and no terracing. Generally, if you wanna get slightly technical the rim to the floor depth is 1/5 of the diameter. [caption id="attachment_2437" align="aligncenter" width="421" caption="Simple crater"]Simple crater[/caption] Complex craters
    These are the most common ones in the solar system and are seen on the moon and other bodies. The main difference between complex craters and simple craters is the gravity of the body being hit and the strength of the target material. These two things will produce craters that are two kilometres in diameter if they land in soft sediments on the Earth and 4 km if they land in much more substantial rock on the Earth.
    On the moon it is a bit of a different story as the moon has only has one sixth of the Earth's gravity. Therefore a larger asteroid or comet is needed to reduce a complex crater with the correct characteristics. The size that is needed is 10 km to about 20 km. If you saw one of these coming towards you on the Earth it would be a good idea to put your head between your legs and kiss ... On Mercury the gravity is one third that of the Earth's so smaller asteroids or comets are needed to create the characteristics of a complex crater. The impactor needed tends to be around 7 km in diameter. [caption id="attachment_2438" align="aligncenter" width="421" caption="complex crater"]complex crater[/caption] Elongate craters These are special type of crater that depends on the angle of the impact of the asteroid or comet with the surface. Most impact craters are circular as described in my previous post but at 10° to the surface the impactor tends to glance off and cause a crater that is elongated. The objects that produce elongated craters aren't small and tend to be bigger than you would think. [caption id="attachment_2439" align="aligncenter" width="512" caption="elongate crater"]elongate crater[/caption]
    Multi-ring basins
    These are some of the biggest craters that are found in the solar system. They are produced by the impactor hitting the hard, rigid surface and causing ripples in the layer beneath the surface (the asthenosphere). The asthenosphere is plasticky and viscous and moves in response to the impact. The layer above the asthenosphere, the lithosphere, ripples but is much firmer and rigid and therefore cracks form. These cracks form in circles around the impact. [caption id="attachment_2440" align="aligncenter" width="500" caption="multiring basin"]multiring basin[/caption] That's all the different types of craters that you may come across in the solar system. Outside of the solar system, who knows? It would be nice to spot some of these craters with your telescope or binoculars or even your eyes. On the Earth craters are hard to spot because of erosion and weathering but it is possible although in some cases you have to have quite an imagination. Poor a list of all the craters on earth that is regularly updated you might like to try the impact cratering database.
    Some of the indicators to look for when looking for an impact crater-
    The first is basically flat quartz and the second is only produced by comets, asteroids and meteorites in the Earth and forming impact craters. These features are not shown by any other geological process so this area is certain to be an impact crater. Glass is obviously found on Earth but is a very good indication of an impact crater and is formed by the shock of the impact melting the rock.
    It is possible to see craters on the moon with the naked eye but if you get a pair of binoculars or even a telescope much more can be seen. One of the very best places to look is the Internet as there are superb images as for most of us places such as mercury and Uranus are inaccessible. Now that you are a crater expert you can really interest your friends telling them about the latest craters and get some street cred in the, err, crater geek world.
    ]]>     Mon, 15 Mar 2010 11:57:05 +0000     chris Dann on How impact craters are formed http://www.weirdwarp.com/forum/blog-posts/how-impact-craters-are-formed/#p108 Blog Posts http://www.weirdwarp.com/forum/blog-posts/how-impact-craters-are-formed/#p108 Mon, 08 Mar 2010 11:01:39 +0000 chris Dann on Volcanoes on Earth and Beyond http://www.weirdwarp.com/forum/blog-posts/volcanoes-on-earth-and-beyond/#p107 Blog Posts http://www.weirdwarp.com/forum/blog-posts/volcanoes-on-earth-and-beyond/#p107 Mon, 01 Mar 2010 12:30:47 +0000 chris Dann on Best Of The Week Podcast- http://www.weirdwarp.com/forum/blog-posts/best-of-the-week-podcast/#p106 Blog Posts http://www.weirdwarp.com/forum/blog-posts/best-of-the-week-podcast/#p106 A great lecture with slides from the Royal Society. ]]> Thu, 25 Feb 2010 10:13:55 +0000