Talk:Heat Shield Rock

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Comments[edit]

"Meridiani Planum, the part of Mars where this meteorite was found, is suspected to have once been covered by a layer of material with a thickness of as much as 1 km which has been subsequently eroded. This means that on impact this meteorite might have created a crater, but evidence of that crater may have been subsequently erased by millions, or even billions, of years of erosion. In any case, the meteorite does not show much signs of rust despite Mars's oxidizing environment, so it either fell recently or was buried until recently. It also shows little signs of weathering or exposure to water."

It seems contradictory that the meteorite's crater took "millions, or even billions, of years" to erase yet the meteorite "fell recently". Buried I could understand if the meteor created a crater and was simultaneously buried, becoming unearthed recently by coincidence. Am I misinterpreting the text? blahpers 21:08, 2005 Jan 21 (UTC)

It either fell recently or was buried until recently. We have no way to tell. It might have fallen recently, but been slowed down sufficiently by Mars's atmosphere that it didn't make much of a crater when it fell. Since this is the first meteorite ever discovered on Mars (or anywhere outside of Earth), we don't really know much. Opportunity will look for more meteorites, it's on a dry featureless plain, and that's the sort of desert environment where meteorites are most readily spotted on Earth. -- Curps 21:54, 21 Jan 2005 (UTC)
"Mars's oxidizing environment?" Its atmosphere is mostly CO2 and only has traces of oxygen and water. It seems like oxidation would proceed very slowly in Mars's atmosphere... --Pyrochem (talk) 20:22, 18 April 2010 (UTC)

is it iron?[edit]

Is it an iron meteorite? The article seems to make tangential mention of this when talking about drilling, but it's never clearly stated. Deuar 18:49, 18 March 2006 (UTC)

Good question. I'm guessing that no one knows for sure. And apparently the only way to find out for sure is to drill into it, which (if it is iron) would permanently damage the drilling tools. So I guess someone decided that drilling into all the *other* rocks had a higher priority. Still, it would be nice to have someone confirm or deny these guesses -- someone who actually understands the drilling protocol. --70.189.73.224 23:15, 5 October 2006 (UTC)
I think the answer is yes. NASA's Mars Exploration Rover Opportunity has found an iron meteorite on Mars, the first meteorite of any type ever identified on another planet. The pitted, basketball-size object is mostly made of iron and nickel. Readings from spectrometers on the rover determined that composition. (from http://photojournal.jpl.nasa.gov/catalog/PIA07269) No drilling needed. —dto (talkcontribs) 06:50, 6 October 2006 (UTC)
Yea, the rover stuck the Mossbauer Spectrometer up to the rock and they determined its composition from that. -- Riffsyphon1024 22:20, 6 October 2006 (UTC)

[1] gives a composition of the meteorite of mostly iron with nickle concentration between 5% (Mössbauer) and 7% APXS. The mössbauer identifies kamacite as alloy. --Stone 12:12, 22 May 2007 (UTC)

No meteorites on moon? / first on another solar system body?[edit]

I quote the article http://en.wikipedia.org/wiki/Meteorite : "More generally, a meteorite on the surface of any celestial body is an object that has come from elsewhere in space. Meteorites have been found on the Moon[1][2] and Mars.[3]" And the first reference is : "McSween, H.Y. Jr. (1976) A new type of chondritic meteorite found in lunar soil. Earth and Planetary Science Letters 31, 193-199". Unless the Moon doesn't count as a solar system body, both claims seem incorrect --84.58.30.117 18 November 2006

HSR isn't evidence for water or dense atmosphere[edit]

Some of this entry, and the Fairen et al. paper it is based on (http://onlinelibrary.wiley.com/doi/10.1111/j.1945-5100.2011.01297.x/abstract;jsessionid=6F7CFE68B11CA4B54C5BB7873B47F9A6.d03t04), is rather misleading about the current state of affairs, particularly about the current thinking about the timing of HSR's arrival on Mars and it's exposure to water on Meridiani Planum.....

1. It is argued that HSR arrived billions of years ago, when Meridiani Planum was wet, warmer, and Mars had denser atmosphere. But there is nothing about HSR that proves this or really even suggests it. For example, to survive impact as undamaged as HSR is (and there IS no evidence of any damage) HSR would have had to impact at less that 2km/s, and probably less than 1 km/s. For this to happen, it has been shown (http://jchappelow.saga-inc.com/Heat%20Shield%20Rock1.pdf) that HSR would also HAVE to impact at a VERY shallow angle, probably less than 5 deg. Not only would this not leave much of a crater, but the ricochet of the meteorite at this sharp an impact angle would have carried it 100s of meters from whatever impact mark it did make. Thus the absence of a 'crater' near HSR does not say anything about how long it may have been on Mars.

2. Similarly, there is no reason to believe that a "soft, wet surface" would be needed for, or even would favor, HSR's survival of impact. As stated above, to survive impact in such good shape, it would have had to impact at low speed and very shallow impact angle. And this does not require a soft, wet surface, either. And even if it DID, Meridiani Planum is COVERED in soft, DRY dust and sand dunes that could fit any such requirement just as well.

3. There is also no need to invoke a denser atmosphere to explain HSR. Chappelow and Sharpton (http://jchappelow.saga-inc.com/Heat%20Shield%20Rock1.pdf) showed that even Mars' current atmosphere could slow HSR down sufficiently to survive impact. In fact even the much larger Block Island meteorite could also be so decelerated by today's atmosphere (http://jchappelow.saga-inc.com/BlockIslandPaperFinal.pdf). Thus the argument that a denser atmosphere would be needed, and that this would imply an arrival date in the Noachian, is just plain wrong.

4. In addition, there is a good reason to believe that HSR must have arrived AFTER Mars had become the dry, arid, almost airless place it is today: In the presence of liquid water, metallic iron would chemically weather down to nothing very quickly in geological terms. Not only has this not happened, but the fairly intact condition of the REGMAGLYPTS covering HSR argues that it has NEVER been exposed to liquid water. No need to invoke some complicated argument about it landing in the wet mud, but then somehow being protected from exposure to water; it just simply landed later and was never exposed. Easy. Occham's Razor wins again.

5. And finally, there is no evidence on any of these meteorites to suggest they have undergone the extensive mechanical weathering they would be expected to have if tens to hundreds of meters of material had been eroded from around them. Thus it is likely that they have been in place no longer than the last episode of extensive erosion in Meridiani. This is thought to have occurred AFTER Mars climate had changed to cold and dry.

Thus the argument that HSR has been on Mars since the Noachian collapses. It certainly is not generally accepted in 'the community'. Indeed, the EVIDENCE indicates that HSR (and the other meteorites) has landed much more recently. I think that the whole 2nd paragraph in this entry should be lifted out of it.... Ferrocephalus (talk) 08:12 UTC, 25 July 2012

Retitle article[edit]

I suggest that we retitle this article by using its proper name, rather than the current generic and unspecific title. It seems more logical to call it Meridiani Planum meteorite. Please discuss. If this has been discussed before, or if there is any guideline to look at, please point me in that direction. -- Brangifer (talk) 06:04, 28 April 2013 (UTC)