[X] My Assistant

[Guest_Sunspot_*]

http://marsrovers.jpl.nasa.gov/spotlight/o...y/20050427.html

Opportunity Discovers Tiny Craters on Mars

[tty]

Have a look at this:

http://www.cosis.net/abstracts/EGU05/02197/EGU05-J-02197.pdf

sounds like at least small-scale lightning strikes might be possible

[Guest_Edward Schmitz_*]

Have a look at this:

http://www.cosis.net/abstracts/EGU05/02197/EGU05-J-02197.pdf

sounds like at least small-scale lightning strikes might be possible

Wow! Good work. I still wouldn't bet the farm on it. But I think it sounds more plausible than a rock that just barily made it to the surface from space.

If it were a meteor, there should be a normal distribution of craters. Few large ones, more mid-sized, and lots of small ones. But the distibution stops abruptly after a certain point.

The other thing is that after it left endurance, they inspected the tracks they made six months earlier. It showed significant modification. The landscape is active. That crater probably happened in the last few years. Centuries at the most.

[Guest_Richard Trigaux_*]

Interesting discution about those strange little pits.

They look like the pits formed by certain insects to catch ants. Those insect pits are of course funnel-shaped, but I think that it those martian pits were made from sand flowing into a cavity, they would be larger, or much more blunt, from the thickness of the sand in this place. Such were the pits near Anatolia: much larger.

About electric discharges, on Earth they can occur at very high altitude, between the highest cumulonimbus and the ionosphere. But these discharges do not look like classical lighning: rather sorts of flames, and not very bright, this explaining they were discovered only recently. So there is an abrupt transition in air property, at a given pressure, far above Mars pressure: under this pressure, electric discharges are corona like, above they are lighning-like. So I think it is difficult to have large lighning on Mars, powerfull enough to make such pits.

About lighning pits observed by John M Dollan, I would be curious to see their shape: funnel without rim, or crater with rim? The explosion formed by a lighning would be very similar to the one formed by a meteorite, so the comparison is interesting. Anyway the smallest craters observed on the Moon had no rim, as there is a strong scale effect in crater shape: small craters above 10m are just holes, without rims, as the material would be ejected at distances far superior to the diametre.

So I think the pits are meteorites impacts, but as noticed by Edward Schmitz, their distribution is not what we could expect. But we have a very small sample, and also meteorites often travel in groups, so the pits could have formed together.

Pity they did not made close images, after certain images I had an impression that the largest pit contained a stone, which would had be thrown here by a larger impact, as the "bounce " stone. Simplest explanation.

[John M. Dollan]

About lighning pits observed by John M Dollan, I would be curious to see their shape: funnel without rim, or crater with rim? The explosion formed by a lighning would be very similar to the one formed by a meteorite, so the comparison is interesting. ...

From what I recall, there was no rim. It looked very similar to an ant lion's pit, albeit a bit larger (maybe 6 inches? It's been a LONG time...). There was a fulgerite directly beneath it, however, so I'm certain that it was formed by lightning.

...John...

[Guest_Richard Trigaux_*]

Thanks John for your precisions. As I expected, your lightning impacts had no rim, as the tiny martian pits. So it strengthen the idea of small explosion pits, althought it does not disprove that those martian pits were lightning impact pits.

By the way it is about ant lions I was speaking.

As far as I know fulgerites are alway formed by lighning, they are tubes (often hollow) of glassy molten rock that we can find on the lightning path into the soil, so it is not astonishing to find them directly under an inpact, right on the countrary it makes surer that the pits you found were lightning impacts.

Richard

[Marcel]

Thanks John for your precisions. As I expected, your lightning impacts had no rim, as the tiny martian pits. So it strengthen the idea of small explosion pits, althought it does not disprove that those martian pits were lightning impact pits.

By the way it is about ant lions I was speaking.

As far as I know fulgerites are alway formed by lighning, they are tubes (often hollow) of glassy molten rock that we can find on the lightning path into the soil, so it is not astonishing to find them directly under an inpact, right on the countrary it makes surer that the pits you found were lightning impacts.

Richard

Wowowow, don't forget that there are more ways to make a hole in the ground. I don't believe discharges in the Martian atmosphere can be powerfull enough to displace material in this manner. Simply, because there's not enough molecules to make the amps (and thus watts, and thus Joules per second) go through ionized channels.

Since there's no rim around this features, my vote would be that it is material that somehow collapsed into voids underneath.

But i'm not sure.....

[dvandorn]

Wowowow, don't forget that there are more ways to make a hole in the ground. I don't believe discharges in the Martian atmosphere can be powerfull enough to displace material in this manner. Simply, because there's not enough molecules to make the amps (and thus watts, and thus Joules per second) go through ionized channels.

Since there's no rim around this features, my vote would be that it is material that somehow collapsed into voids underneath.

But i'm not sure.....

The freshest of the tiny craters we've seen in these dunes *does* have a raised rim, though.

I just have to figure these are little secondary impact craters, caused by small stones ejected from a larger impact somewhere nearby. Either that, or the freshest ones *may* be from stray bolts, nuts or flakes of paint that came off the lander's cruise stage and survived to hit the ground. But that last is *awfully* hard to prove.

-the other Doug