Mercury in closeup - Kuiper and more

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

This stunning view is Kuiper* crater, the central feature in the image from last Tuesday. The crater itself is 62km in diameter (39 miles) but the ejecta from the impact fan out over a much greater distance.

The Messenger website observes:

Bright ejecta rays such as these are produced as impacts excavate and eject relatively unweathered subsurface material. The ejecta rays of Kuiper and other large craters are observed to extend for hundreds of kilometers across the cratered terrain of Mercury

But the real guy responsible for the rays is here:

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

This is the (as yet unnamed?) crater at about 1 o'clock in Tuesday's image. Measuring about 110km across (68 miles) the central impact has spread ejecta over half the planet.

Again from the website:

A striking characteristic of this newly imaged area is the large pattern of rays that extend from the northern region of Mercury to regions south of Kuiper. This extensive ray system appears to emanate from a relatively young crater newly imaged by MESSENGER, providing a view of the planet distinctly unique from that obtained during MESSENGER’s first flyby. This young, extensively rayed crater, along with the prominent rayed crater to the southeast of Kuiper, near the limb of the planet, were both seen in Earth-based radar images of Mercury but not previously imaged by spacecraft.

Yeah, but what do they mean by young?
---------------
*Named in honour of Gerard Kuiper, he of Kuiper Belt fame. Though is seems he had bugger all to do wih it really. Grow into these trousers... >>

Mercury in focus

Phil Plait says it much better that I ever could:

"Holy Haleakala. Look at those rays! They go all the way across the planet!"

Go read his first report. Grow into these trousers... >>

MESSENGER fly-by of Mercury

Earlier today the Messenger spacecraft flew past the planet Mercury (images to follow as they are released).
The photo here is ~15h before closest approach
Credit NASA / APL

This is a long term and complicated mission...
Launched in 2004 Messenger aims to go into orbit around Mercury in 2011 and collect data for a whole year.

Remember, Mercury is the closest planet to the Sun. If you were to aim a craft directly, the Sun's enormous gravitation would cause so much acceleration that the craft could not carry enough fuel to slow down in time to enter mercurial orbit.

So what do you do? You launch it sideways into orbit around the Sun, use gravity assists (flybys) and short engine burns (using the precious fuel) to gradually nudge the craft into a diminishing solar orbit until it is captured by the gravitation field of Mercury.

From the mission website:

To become the first spacecraft to orbit Mercury, MESSENGER must follow a path through the inner solar system, including one flyby of Earth, two flybys of Venus, and three flybys of Mercury. This impressive journey will return the first new spacecraft data from Mercury since the Mariner 10 mission over 30 years ago.

See the Messenger site for this timeline of the mission:


One more Mercury fly-past (29th Sept. 2009) and two more fuel burns (DSMs - Deep Space Maneuvers) before it goes into orbit (18th Feb 2011). Grow into these trousers... >>