News from the Winged Messenger

Dr, Solomon describes what MESSENGER learned about the surface of Mercury.
Dr, Solomon describes what MESSENGER learned about the surface of Mercury.

When we can learn more about one of our companion planets, that has to be counted as a good day.  Recently, images have been coming from Pluto, the body that use to be called our ninth planet.  Now just a dwarf planet, Pluto is slowly giving up its secrets. But volcanism? Lots of sulfur on the surface?

For that news and more, we have to travel about 39 Astronomical Units towards the center of our solar system, to the planet Mercury.  Dr. Sean Solomon shared some of the exciting discoveries from the smallest planet of our solar system at the annual Astronomy Day public lecture at the Jamestown campus of Guilford Technical Community College about a week ago.  We heard about the troubles caused by the Sun when trying to achieve orbit around the innermost planet, and some interesting aspects of the surface of that sun-baked body.  For the mission’s official website go to

Dr. Solomon, with Lamont-Doherty Earth Observatory, Columbia University, is the Principal Investigator in charge of the MESSENGER mission to Mercury.  That NASA space probe spent 4 years in orbit around Mercury, and Dr. Solomon was prepared to share some of its secrets.

Hallows in the polar craters appear to be protecting water ice on Mercury.  There is evidence of volcanism on the planet.  The surface has lots of sulfur, and the planet has contracted in radius between 5 and 8 kilometers.

Dr. Solomon began his presentation describing a little about the problem of getting a space probe to Mercury and putting it into orbit around that planet.  I hadn’t given the heat from the Sun much thought, so sure, the probe design team would have to strengthen the shielding to keep circuits from overheating.  But the effects of the Sun’s gravity surprised me the most.  This would make getting into orbit a real challenge.

MESSENGER's long and winding road to Mercury
MESSENGER’s long and winding road to Mercury

If we launched straight towards Mercury the momentum of the spacecraft would be increased by the pull of the Sun.  Much fuel would have to be expended to slow down for orbital insertion.  And that fuel is expensive to launch from Earth, so a better way needs found.

It takes about 9 months for a space probe to get to Mars from Earth.  To compensate for the effects of the Sun’s gravity, it took MESSENGER 7 years from launch to orbit!  Those seven years included one Earth flyby, two Venus flybys, and three Mercury flybys!

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