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Mars outcrops breccia instead of conglomerate? Water not needed?
NASA is claiming that it has found conglomerates on Mars based on some deposits that have been found by the new Curiosity Mars rover. They are using this claim to go on to assert that water must have flowed across the planet, despite the current atmospheric conditions precluding water.
Couldn't those outcrops be more plausibly consist of breccia whose exposed clasts have been rounded remove their original angular morphology so the exposed examples resemble pebbles?
The breccias could plausibly have been deposited during volcanic eruption or be due to impact shock from ancient asteroid strikes (Mars is close to the asteroid belt, and there is ample evidence of volcanism on Mars). Hence there is no need to claim a watery past for Mars.
See this article for example (including images):
2 個解答
- ?Lv 79 年前最愛解答
I as well have thought about it and part of the problem is that we do not know what the "conglomerate" matrix is. The rounding is not the biggest issue, the matrix is. If it is sand or silt it is probably water driven.
The other problem is that we do not know what the age of the rock actually is. Is it 4.7 Billion Years old, and if so what was the state of the atmosphere and proto lithosphere? What was the temperature at formation? What was the pressure of formation, was the atmosphere water or some other lliquifiable gas? Was there superheated mantle gases that could have caused volcanic exhalitives to act as a carrying agent ?
I think the comment that the conglomerate "fluid" carrying agent was water, may actually be fairly speculative.
Having said this, the deposits do actually look like outwash fan conglomerates or flood conglomerates associated with braided streams/ glacial runoff. These do not look like pervasive regional deposits controlled by seasonal rainfall.
- JamesLv 49 年前
Breccias are ubiquitous on mars. Why would only these be rounded by weathering? Its unlikely.
