Mgs News Briefing On September 20, 2005, interesting changes observed... Options

[Guest_RGClark_*]

Wow! New craters and New gullies??

The explanation on this page suggests it's a dry flow:

PIA04290: New Gullies on Martian Sand Dune.
http://photojournal.jpl.nasa.gov/catalog/PIA04290

Nah, it's a stream baby!



Bob C.

[SigurRosFan]

All new MGS images and caption:

http://photojournal.jpl.nasa.gov/target/Mars

[SigurRosFan]

More:

MOC Celebrates 8 Years At Mars!

Key Science and Recent Changes on Mars: The Value of an Extended Mission for MGS

http://www.msss.com/mars_images/moc/2005/09/20/index.html

Suggestion that the new crater near the Ulysses Patera caldera (about 25 meters diameter) formed in the early to mid 1980's.

[ljk4-1]

More:

MOC Celebrates 8 Years At Mars!

Key Science and Recent Changes on Mars: The Value of an Extended Mission for MGS

http://www.msss.com/mars_images/moc/2005/09/20/index.html

Suggestion that the new crater near the Ulysses Patera caldera (about 25 meters diameter) formed in the early to mid 1980's.

Just to play Devil's Advocate for the sake of science:

http://photojournal.jpl.nasa.gov/catalog/PIA04292

Would the Viking Orbiter imaging system have been able to see such a small crater? Any chance it was covered by dust and uncovered by subsequent winds?

I am certianly not saying that Mars couldn't have been hit by meteorites over the past 20 years - hey, a rover's heatshield landed right next to an iron meteorite - but the Viking image does not look clear/sharp enough to have distinguished such a relatively small crater; but please prove me wrong.

BTW, this and the new gullies shows how team members go through those images with a microscopic comb.

[dvandorn]

I think it's pretty clear that the crater was not there nearly 30 years ago, that it was very fresh when first imaged by MGS, and that its ejecta has been significantly lightened in albedo since it was first imaged.

There is a lower-resolution image at this same site that shows the area at the same resolution available in the Viking image, and you can easily see the dark ejecta. And we can see that the dark ejecta has been lightened considerably between the first and second MGS images -- I can't imagine that this ejecta would get lighter, then darker, then lighter again. That's counter-intuitive to aeolian alteration; even when things are covered then uncovered, the fines would tend to remain, and the fine feathery ejecta pattern visible in the "fresh crater" image would be lost forever.

No, it's awfully obvious that this is a very fresh impact crater. And there's no reason to believe that such things don't continue to happen on Mars. It's a big planet, and it's closer to the asteroid belt than we are. There are more impactors nearby, and the thinner atmosphere promotes survival of impactors down to the surface.

-the other Doug

[tedstryk]

Just to play Devil's Advocate for the sake of science:

http://photojournal.jpl.nasa.gov/catalog/PIA04292

Would the Viking Orbiter imaging system have been able to see such a small crater?  Any chance it was covered by dust and uncovered by subsequent winds?

I am certianly not saying that Mars couldn't have been hit by meteorites over the past 20 years - hey, a rover's heatshield landed right next to an iron meteorite - but the Viking image does not look clear/sharp enough to have distinguished such a relatively small crater; but please prove me wrong.

BTW, this and the new gullies shows how team members go through those images with a microscopic comb.

Based on the other features there, I think the answer to your first question is that yes, it could But the question is if it was unburied or new. Based on the appearance of man-made impacts, I would say it is new, but I don't know if something old and exhumed would have the same appearance or not.

[ljk4-1]

I think it's pretty clear that the crater was not there nearly 30 years ago, that it was very fresh when first imaged by MGS, and that its ejecta has been significantly lightened in albedo since it was first imaged.

There is a lower-resolution image at this same site that shows the area at the same resolution available in the Viking image, and you can easily see the dark ejecta.  And we can see that the dark ejecta has been lightened considerably between the first and second MGS images -- I can't imagine that this ejecta would get lighter, then darker, then lighter again.  That's counter-intuitive to aeolian alteration; even when things are covered then uncovered, the fines would tend to remain, and the fine feathery ejecta pattern visible in the "fresh crater" image would be lost forever.

No, it's awfully obvious that this is a very fresh impact crater.  And there's no reason to believe that such things don't continue to happen on Mars.  It's a big planet, and it's closer to the asteroid belt than we are.  There are more impactors nearby, and the thinner atmosphere promotes survival of impactors down to the surface.

-the other Doug

I noticed that the meteorite impacted near the edge of a crater. Did anyone check to see if the crater rim near the impact area was disturbed, such as with boulders rolling down the side?

I also wonder if perhaps the meteorite was from an old spacecraft that fell out of orbit, or one of the final rocket stages?

[volcanopele]

Recently formed impact crater

This new crater, ~25 m across according to the caption, is about the size of Eagle, right? Now Eagle crater is nearly filled with sand and it would be interesting to see if HiRISE could get a view of this crater to see how quickly it is being covered with sand...

[Bob Shaw]

It's a big planet, and it's closer to the asteroid belt than we are.  There are more impactors nearby, and the thinner atmosphere promotes survival of impactors down to the surface.

-the other Doug

other Doug:

I think the process may be a bit more complex than that.

Yes, Mars is closer to the asteroid belt, that's a given.

But, I suspect in that case that it has already swept up more of the possible impact candidates than it would have if it were in Earth's position. Contrariwise, Earth is bigger, and far more massive, so will tend to disturb any trajectories more than Mars would. Also, Earth 'sweeps up' objects faster than Mars, because of it's smaller orbital diameter (more chances of a body in an elliptical orbit coming close).

The bottom line: it's a confusing situation, full of contradictions!

Add in the higher-reaching Martian atmosphere, and the fact that 70% of Terrestrial craters occur in, er, water, and it's a helluva calculation. But a complex one, and one that may even have a counter-intuitive outcome...

Bob Shaw

[SigurRosFan]

... is about the size of Eagle, right? ...

Yes. Eagle is 22 meters across.

[Marz]

Nice to see images that show that Mars is alive.

It was exciting to see the recent activity, but at the same time, I wanted more. That CO2 could explain many recent fluvial activities is in some ways a let down, since I was hoping for more signs of water seeps...

And when I first saw the image of the huge volcano, I was jumping to conclusions that they found evidence of recent activity, not a crater. Methane gas, hot water springs, giant spiders building pyramids to Elvis.... I realize this crater is an important temporal yardstick, but boy was I expecting some real martian cheeze!

[Guest_BruceMoomaw_*]

I have to say that I was disappointed by the new news -- I was expecting to see a new water-formed canyon gully. Oddly, the most important piece of news may be one that nobody's mentioned yet: the new count of the rate at which craters are forming on Mars suggests that, since the Solar System's early days, the impact rate may be only 1/5 of what had previously been estimated! ( http://photojournal.jpl.nasa.gov/catalog/PIA04292 ) If so, most of Mars' surface may be a lot older than had previously been estimated.

[Guest_RGClark_*]

I have to say that I was disappointed by the new news -- I was expecting to see a new water-formed canyon gully...

You should be disappointed only if the proffered explanation is the correct one. The gullies seen on sand dunes prior to this were believed also to be due to liquid water. It is only when they are seen to be produced currently that the suggestion is made by Malin that they are due to gas release.
However, there has been published research that the gullies can be produced under current conditions:

Water Flowed Recently on Mars, NASA Scientists Say.
By Robert Roy Britt
posted: 24 August 2005
"If liquid water pops out onto Mars' surface, it can create short gullies about 550-yards (500-meters) long," Heldmann said in a statement. "We find that the short length of the gully features implies they did form under conditions similar to those on present-day Mars, with simultaneous freezing and rapid evaporation of nearly pure liquid water."
http://www.space.com/scienceastronomy/0508...rs_gullies.html

Formation of Martian Gullies by the Action of Liquid Water Flowing under Current Martian Environmental Conditions.
American Astronomical Society, DPS meeting #37, #32.10
"We find that, contrary to popular belief, the fluvially-carved Martian gullies are consistent with formation conditions such as now occur on Mars, outside of the temperature-pressure stability regime of liquid water.
... our model indicates that these fluvially-carved gullies formed in the low temperature and low pressure conditions of present day Mars by the action of relatively pure liquid water.
http://adsabs.harvard.edu/cgi-bin/bib_quer...DPS....37.3210H

Formation of Martian Gullies by the Action of Liquid Water Flowing Under Current Martian Environmental Conditions.
36th Annual Lunar and Planetary Science Conference, March 14-18, 2005, in League City, Texas, abstract no.1270.
http://adsabs.harvard.edu/cgi-bin/bib_quer...LPI....36.1270H

Formation of Martian gullies by the action of liquid water flowing under current Martian environmental conditions.
Journal of Geophysical Research, Volume 110, Issue E5, CiteID E05004.
http://adsabs.harvard.edu/cgi-bin/bib_quer...JGRE..11005004H


Bob Clark

[Guest_BruceMoomaw_*]

Oh, I'm well aware of the fact that that new gully could be melted ice -- after all, a lot of it is already believed to exist within many of Mars' polar-region dunes. Even if it is, though, it's a less impressive phenomenon than a new gully bursting out of one of the rock strata on the sides of the channels would be.

[Guest_spaceffm_*]

Nobody has seen this cool gif animation?
Is it Ice under the ground?



http://photojournal.jpl.nasa.gov/archive/PIA04295.gif