Starship Asterisk*

The Great Crater Hokusai

Explanation: One of the largest young craters on Mercury, 114 kilometer (71 mile) diameter Hokusai crater's bright rays are known to extend across much of the planet. But this mosaic of oblique views focuses on Hokusai close up, its sunlit central peaks, terraced crater walls, and frozen sea of impact melt on the crater's floor. The images were captured by the MESSENGER spacecraft. The first to orbit Mercury, since 2011 MESSENGER has conducted scientific explorations, including extensive imaging of the Solar System's innermost planet. Now running out of propellant and unable to counter orbital perturbations caused by the Sun's gravity, MESSENGER is predicted to impact the surface of Mercury on April 30.

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Outstanding!

Because I don't have anything to say other than "Wow!"
I just thought I'd throw Wikipedia's entry on the Hokusai crater out there.

http://en.wikipedia.org/wiki/Hokusai_%28crater%29

Scott

And it was doing so well too....

Time to send another one!!!

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More on MESSENGER http://asterisk.apod.com/viewtopic.php?t=34671

Why do many craters seem to be flat? Shouldn't they be more like cone shaped?

That actually looks like a peak-ring crater very close to the transition from simple peak to peak-ring morphology.

vsolo wrote:Why do many craters seem to be flat? Shouldn't they be more like cone shaped?

Small craters are bowl-shaped, but rocks are not strong enough to support crater walls many kilometers tall. Also, the crater floor rebounds after the shock wave passes and the crater walls slump in along curving faults to create the terraces. If the crater is big enough, the floor actually rebounds to form a central peak. In bigger craters, like this one, the central peak is too large to support its own weight and collapses to create a ring of peaks. On Mercury, lots of craters are also filled with lava (like lunar Plato or Archimedes) or impact melt.

vsolo wrote:Why do many craters seem to be flat? Shouldn't they be more like cone shaped?

Oddly enough this crater is large enough for the floor not to be flat due to the curvature of the planet's surface. (it's not a very big planet, so that is easy).

ps. Does anybody know of a source describing impacts on increasingly curved surfaces? I'd love to see some simulations.

Truly breathtaking, it's astonishing what can be achieved in space exploration. Really excited about New Horizons!!!

Congratulations to all involved for the successful mission.

It amazes me that the likely end of the mission can be determined to within a 5 minute interval , as in the information brought up through the "impact the surface of Mercury" link it states "the highly successful orbital mission is about to come to an end, as the spacecraft runs out of propellant and the force of solar gravity causes it to impact the surface of Mercury, estimated to occur between 3:25 and 3:30 p.m. EDT on April 30, 2015" though adding "The uncertainties associated with low-minimum-altitude operations and near-zero amounts of usable spacecraft propellant introduce the potential for Mercury impact earlier in April or up to one 8.3-hour orbit later – just before midnight EDT on April 30, 2015" but even if that is the outcome it is still an amazing accuracy.