Added 2 new A* pages:The 18th of this month will be a relatively exciting day in space exploration, as that's the day on which the MESSENGER spacecraft ("MErcury Surface, Space ENvironment, GEochemistry and Ranging" -- man, those NASA people have gotten pretty good with acronyms) will go into its orbit of the planet Mercury. NASA's MESSENGER page has a countdown clock for those who like to be exactly on the button on these things.
MESSENGER is only the second craft to visit the innermost planet, the other being Mariner 10 in the mid-70's; MESSENGER will actually orbit the planet, unlike Mariner 10, which could only do three fly-bys. MESSENGER, which left Earth in 2004, has already completed three flybys of the planet, the first about three years ago; it's also made an Earth and two Venus flybys in its long fall toward the Sun:
image by NASA (source)
("DSM" there stands for "Deep-space maneuver.") Because of the Sun's gravitational pull, and Mercury's high speed (49 km/s vs Earth's 30), it's pretty tricky to get into orbit around the planet! Its been using these flybys to help slow it down for the upcoming orbital insertion. It's also been using them to do some scientific studies, and snap some nice pictures. Here's its flyby of Earth in 2005; in the 24-hour period shown here, it went from 66,000 km away from Earth to about 436,000 km away:
video on Youtube
(on YouTube)
Man, I love that video. Other cool images taken by MESSENGER include:
Lava-flooded craters and smooth volcanic plains visible in this mosaic image show that volcanism played an important role in Mercury's history:
image by NASA (source)
This shot from the second Mercury flyby revealed huge impact rays from a previously un-named crater (not sure if it has a name yet):
image by NASA (source)
Approach in the third Mercury flyby, the last (false-)color image it will take before orbit:
image by NASA (source)
In that third flyby on September 29, 2009, somewhere near its closest approach of ~200 km to the planet, MESSENGER unexpected went into "safe mode" for seven hours. :o
A view of the Earth and Moon (lower left) from 183 million km away:
image by NASA (source)
That last shot was part of MESSENGER's unsuccessful scan for vulcanoids: asteroids hypothesized to exist in the gravitationally stable area inside Mercury's orbit; asteroids have been found in every gravitationally stable area of the solar system *except* that one, so it's possible that something else cleared them out during the formation of the solar system.
There's also this mosiac it took in November of last year, which caught all of our solar system's planets except for Uranus and Neptune--and if you look closely at the photos on the lower right side, you can see the telltale stamp of the gas and dust clouds between us and A*!
So MESSENGER's already done some pretty cool stuff; we'll have to see what it comes up with once it enters the first-ever orbit of Mercury in two and a half weeks!
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