NASA Images Suggest Water Still Flows on Mars |
NASA Images Suggest Water Still Flows on Mars |
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Dec 4 2006, 09:25 PM
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Guests |
Dec. 4, 2006
Dwayne Brown/Erica Hupp Headquarters, Washington 202-358-1726/1237 Guy Webster Jet Propulsion Laboratory, Pasadena, Calif. 818-354-6278 MEDIA ADVISORY: M06-186 NASA SCHEDULES BRIEFING TO ANNOUNCE SIGNIFICANT FIND ON MARS WASHINGTON - NASA hosts a news briefing at 1 p.m. EST, Wednesday, Dec. 6, to present new science results from the Mars Global Surveyor. The briefing will take place in the NASA Headquarters auditorium located at 300 E Street, S.W. in Washington and carried live on NASA Television and www.nasa.gov. The agency last week announced the spacecraft's mission may be at its end. Mars Global Surveyor has served the longest and been the most productive of any spacecraft ever sent to the red planet. Data gathered from the mission will continue to be analyzed by scientists. Panelists include: - Michael Meyer -- Lead Scientist, Mars Exploration Program, NASA Headquarters, Washington - Michael Malin -- President and Chief Scientist, Malin Space Science Systems, San Diego, Calif. - Kenneth Edgett -- Scientist, Malin Space Science Systems - Philip Christensen -- Professor, Arizona State University, Tempe, Ariz. |
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Dec 6 2006, 08:27 PM
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Junior Member Group: Members Posts: 21 Joined: 31-January 05 From: Havre, MT Member No.: 163 |
Considering the rate that the Earth intercepts meteors, and adding to that Mars' thinner atmopshere, would it not stand to reason that impacts would reach the surface much, much more often?
And if that is true, what does it say about those regions that are relatively crater-free? Could there be some active geology involved, or are Martian aeolian forces enough to erase some of these smaller craters? ...John, curious as always... -------------------- "To make an apple pie from scratch, you must first create the universe..."
-- Carl Sagan |
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Dec 6 2006, 11:23 PM
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Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
Considering the rate that the Earth intercepts meteors, and adding to that Mars' thinner atmopshere, would it not stand to reason that impacts would reach the surface much, much more often? The rate is higher but it's not as high as you might think given the difference in densities at the surface. The martian atmosphere is extremely thin and at the surface is comparable to the Earth's at around 35KM but because of the lower martian gravity it's scale height is higher (~11km vs ~6km for earth) it is remarkably similar in density to the Earth's atmosphere once you get above 75km or so if I remember correctly. For the most part it filters out a similar amount of "stuff". By similar I'd guess we're talking about a similar order of magnitude here but I'd have to do some digging to get a number I'd be willing to defend. The percentage that reaches the ground is higher for another reason that could well be as important - the average atmospheric impact speed at mars orbit is slightly slower (5-10km/sec slower) and so there is less energy to dissipate. For asteroidal debris this is quite significant as the impact speed can be as low as 7km/sec at mars (vs ~17km/sec typically for Earth) so only about 17% of the energy needs to be disipated. Cometary and retrograde impacts are a different animal and the difference at Mars for these (compared to earth) is 80% and 50% respectively. The main reason there are more apparent craters on Mars is that the surface is (for the most part) really and truly ancient and erosion rates are many orders of magnitude slower than on earth. |
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Dec 6 2006, 11:31 PM
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Junior Member Group: Members Posts: 21 Joined: 31-January 05 From: Havre, MT Member No.: 163 |
The rate is higher but it's not as high as you might think... Thanks for that clarification. It definitely helped me with an off-list discussion. ...John... -------------------- "To make an apple pie from scratch, you must first create the universe..."
-- Carl Sagan |
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