Earth Smiles for Interplanetary Paparazzi

Grin at Mercury!

Not only can you smile at Saturn tomorrow (Friday, July 19), but you can also grin at Mercury.  The scientists using the MESSENGER mission to study the closest planet to the Sun will also capture Earth photobombing the view of the region around Mercury. They’re actually looking for any natural satellites the planet may have and realized that Earth will also be making a cameo appearance in images taken on Friday and Saturday  at 7:49 a.m., 8:38 a.m. and 9:41 a.m. EDT (11:49, 12:38 and 13:41 UTC). If the Sun is in the sky during any of these times and reasonably well above the horizon, then it’s your time to shine and wave for the cameras. Just don’t look at the Sun!  Mercury is about 12 degrees from the Sun, too close to be seen with the unaided eye.

Don’t forget to wave for Saturn, too. Check out my previous entry for details!

If you haven’t heard of MESSENGER before, the name stands for MErcury Surface, Space Environment, GEochemistry, and Ranging mission, and it sent the the first spacecraft to orbit Mercury. It has been studying the planet closeup for a few years now, and in that time has mapped the surface and provided many new insights into Mercury’s cratering rates, internal structure, and “weather” characteristics. Because the surface is so heavily cratered, it’s clear that the planet hasn’t been active (geologically) for billions of years (since the period called the Late Heavy Bombardment. Mercury is a very dense planet, with dense iron-rich core that is very likely still molten. Nobody expected Mercury to have much of an atmosphere, but it turns out that it does have a very tenuous cloud of material around it made up of hydrogen, helium, sodium, calcium and potassium. It’s very likely that this so-called “exosphere” is continually replenished by interactions between the solar wind and the surface of the planet.  There’s also a possibility that water exists on Mercury, but only in the polar regions that never get any direct sunlight. Elsewhere on the planet, surface ice wouldn’t last long; surface temperatures range upwards to around 800° F during the day!  In the early morning times before sunset, the surface temperatures plunge to close to -300!

If you want to know more about MESSENGER‘s explorations of Mercury, check out the mission website. It’s chock full of images and news releases outlining the amazing things planetary scientists are finding out about the closest planet to the Sun.