Space/Science — HabitableZone

Space/Science » in reply to re: Getting impact chronology straight

Thanks for trying, but...
Nick Hoffman — (archived)

Read your own reference again - < a href="http://www7.nationalacademies.org/ssb/MarsACh04.pdf>http://www7.nationalacademies.org/ssb/MarsACh04.pdf

It says that the uncertainty is has relatively little effect with very old and very young terrains - they are fixed endpoints at ~ the origin of the solar system and ~ now. There is uncertainty in the middle - especially the late Hesperian and Early Amazonian, as the text you quoted makes abundantly clear.

However:-

There is no doubt at all that Hellas is a very old event, predating every single one of the "smaller" craters superimposed on it. (I use quote marks, because many of these are multi-hundred km ring basins in their own right). Hellas is the OLDEST event we can observe on Mars, unless the northern plains are an even more massive and earlier impact, as some authors hypothesise.

Hellas effectively pre-dates the Noachian, since ages are based on observed craters, and the observed craters superpose Hellas. Hellas is NOWHERE NEAR "middle Martian history".

There is no proven nor likely genetic link between Alba Patera and Hellas. There *might* be some sort of link with the old volcanoes around Hellas - Tyrrhena Hadriaca and Amphitrites Paterae, Peneus Caldera.

FYI, look up Herb Frey's recent work on dating of buried surfaces - identifying large craters with MOLA and re-working the dates of surfaces. The Northern Plains have a buried surface with many large impacts, making them older than the onsewrved crater density of the southern Highlands, but the southern Highlands have an EVEN OLDER buried population dating back a tad further, and the major impact basins - Argyre, Isidis, Chryse, and Hellas pre-date even those...

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