Mercury Flyby 2 Options

[SFJCody]

That question is ringing a bell. Wasn't there a new paper out recently saying that Mercury doesn't have impact poles

It's been done? I really should pay more attention!

[Juramike]

Le Feuvre, M, and Wieczorek, M.A. Icarus 197 (2008) 291-306. "Non-uniform cratering of the terrestrial planets". doi: 10.1016/j.icarus.2008.04.011 (freely available here!)

From the article, the authors find about 10% increased cratering at Mercury's poles compared to the equator, and Mercury's cratering flux is about 1.9x that of our moon.

-Mike


[And Emily's right, this was in the September 2008 issue of Icarus]

[SFJCody]

From the article, the authors find about 10% increased cratering at Mercury's poles compared to the equator, and Mercury's cratering flux is about 1.9x that of our moon.

-

Ah, but they only consider cratering rates as a function of latitude, not as a function of longitude.

[Holder of the Tw...]

A news item worth noting in passing. Thanks to the solar sailing technique, the targeting for this flyby was awfully good. In fact, they are claiming it was the most accurate targeting of any planetary flyby other than earth. It came in just a wee bit under 200 km.

MESSENGER News

[Phil Stooke]

Going back to the question about longitudinal variations in cratering, people have been looking for that for decades. I think there are some claims from modelling and some from crater counts, applied to bodies all over the solar system. I don't find any of them convincing. As for Earth focussing impacts on one side of the moon or the other - or, even worse, shading the nearside from impacts - even less convincing. Whatever slight variations there might be are either overwhelmed by saturation cratering or by various geological effects, or they fall into that class of observations which exist only in the statistics, but not in any meaningful way in reality. Show me a visible impact gradient and I'll back down!

Phil

[Phil Stooke]

And here's the new limb view reprojected. There's quite a bit of relief distortion.

Phil

[volcanopele]

The only body I can think of is Triton, where there is a difference in the distribution of craters between the trailing and leading hemisphere.

[ElkGroveDan]

There's quite a bit of relief distortion.

I'll say. That crater on the left looks like a cake pan.

[Phil Stooke]

volcanopele: "The only body I can think of is Triton, where there is a difference in the distribution of craters between the trailing and leading hemisphere."

We have very limited coverage of Triton, not many craters, and an unknown effect from regional variations in geology (Canteloup terrain vs the plains units elsewhere) - it's not a very robust analysis.

Phil

[SFJCody]

Oh well...


Some new pics are up now, including a Mariner 10/Messenger comparison at different phase angles

[tedstryk]

We have very limited coverage of Triton, not many craters, and an unknown effect from regional variations in geology (Canteloup terrain vs the plains units elsewhere) - it's not a very robust analysis.

Phil

I have found the analysis to be relatively good, at least given the coverage we have. However, with Triton being in a retrograde orbit, the reason for the asymmetry may have nothing to do with the reason for the asymmetry on Mercury.

[Phil Stooke]

The limited coverage and poorly understood geology are the keys. If the crater retention age on canteloup terrain is different from that on the plains on the other side of the disk - or even if our ability to identify small craters varies between the two areas - the whole analysis is out the window.

Phil

[Phil Stooke]

Back to Mercury! Some new images released today, including a limb view which I have rectified here.

Phil

[Phil Stooke]

A new limb view, a new reprojection...

Phil

[tedstryk]

These work better with flatter worlds!