Messenger Returns Images of Mercury from Orbit for the First Time.

NASA’s Messenger spacecraft (MErcury Surface,Space Environment, Geochemistry and Ranging) has become the first craft to enter orbit around Mercury and now we have the first picture from orbit.

Mercury by Messenger

Mercury by Messenger

Messenger has taken six years to get into orbit around Mercury. If the Messenger probe had been sent to Mercury on a direct course it would have needed to slow down by an excessive amount which would have required too much fuel. This is because Mercury is so close to the sun that the sun would have accelerated the probe and with Mercury having no atmosphere slowing down would have been a problem.

363 images were taken over six hours and more are expected to be released. The upper part of the picture shows an unsuual, dark rayed crater called Debussy. The lower half of the image shows Mercury’s south pole which has never been seen before by a spacecraft.


So what is the purpose of sending Messenger to Mercury? Well, NASA has set itself six questions to answer.

  • Why is Mercury so dense? Its density gives the impression that Mercury’s metal-rich core occupies over 50% of the planet mass which is twice as great as for the Earth. Messenger will hopefully decide which theory about Mercury’s density is correct.
  • What is the geologic history of Mercury? Only 45% of the surface of Mercury had been imaged at close range until messenger came along. Messenger will investigate the history of Mercury from its images working out its geologic history.
  • What is the nature of Mercury’s magnetic field? Messenger will hopefully answer the question about why the inner planets differ in their magnetic histories.
  • What is Mercury’s core made out of? Measurements of the gravity field and observations by a laser altimeter will give the size of the core and verify that the outer core is molten.
  • What are the materials at Mercury’s poles? There are some unusual material at the polls that are reflective. Could this be ice? This could be quite a discovery as Mercury is very close to the sun.
  • What volatiles are important at Mercury? Mercury’s exosphere  will be measured giving insights into the processes that created it.
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