Along with a description of the search for "vulcanoids," the hypothesized asteroids near the sun, The Planetary Society's Emily Lakdawalla published yesterday this fantastic image from MESSENGER, taken from inside the orbit of Venus. Those two brighter dots in the lower left side of the image? They're Earth and its moon.
The MESSENGER team described the hunt for vulcanoids this way:
No vulcanoids have yet been discovered, and it is not known if any exist. But should they be found, these small, rocky asteroids may yield insights into the formation and early evolution of the solar system. They might contain material left over from the earliest period of planet formation and help determine the conditions under which the terrestrial planets, particularly Mercury, formed. Vulcanoids would also represent an additional population of impactors that contributed to the cratering history of Mercury much more than that of any other body. Impacts by vulcanoids would make the planet's surface appear older, relative to the surfaces of the Moon and other inner planets, than it actually is.
If they do exist, the vulcanoids would be difficult to spot. First, they would be very small – less than 60 kilometers (37 miles) in diameter (a limit set by Earth-based observations) – and their reflected light would generally be drowned out by the bright glare of the nearby Sun. Because of their proximity to the Sun, searches for vulcanoids from the ground can be carried out only during twilight or or dawn or during solar eclipses.
Having made pulse-pounding flybys of the planet, MESSENGER will take up residence in orbit around Mercury on March 18, 2011.
Wayne
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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