Space Topics: MESSENGER
The Year in Pictures: 2008
Mercury as a "Whole New Planet"
Credit: NASA / JPL / CIW / Emily Lakdawalla |
After a journey of three and a half years, MESSENGER
at last gave Earth its first close-up look at Mercury since the final Mariner 10 flyby in 1975.
MESSENGER approached a crescent Mercury, viewing part of the hemisphere that
Mariner 10 had already seen. It swung past the night side and captured a departing
view of territory new to human eyes, including the entire expanse of the Caloris
impact basin, visible in this
enhanced-color image as
a huge orange splotch at
upper right.
The color information from MESSENGER’s camera reveals other oddities.
The floor of Caloris is littered with unusual dark-rimmed craters, which appear
purple here. Other, fresher, craters have lighter interiors and blue sprays
of ejecta. Close examination of the MESSENGER images has lent strong support
to the notion that Mercury has experienced a lengthy history of geologic activity,
including impact cratering,
explosive volcanism, effusive lava flows, and a wholesale shrinking of the
planet due to the ongoing
solidification of a molten metal core. A
second flyby followed on October 30,
and MESSENGER gathered images of most of Mercury that it had not imaged in
the first flyby. One more flyby will take place late next year; the spacecraft
will finally enter orbit and begin its primary mission in 2011.
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