On 10 May, some constraints were leveled upon postHesperian waterflows on Mars. h/t Zimmerman who imputes same to a less-definite past.
Pace Zim this particular paper is all about the "Amazonian" era, or aeon, which Mars is still in, and will remain in until the Sun gets too hot for us down here on Earth. It doesn't even mention the Hesperian 3.7-3.1Gya much less the Noachian.
Which is not to dismiss the paper. It is valuable to know how the postHesperian gullies have formed. For now, is implicated carbon-dioxide. It gets cold in a Martian night, cold enough to make a dry ice of the CO2. This frost, however thin (hardly glacial), suffices over millions of years to carve out the gullies. (But not billions.) One might also consider windbourne dust.
BACKDATE 5/16 whilst we're looking.
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