[Outbackmanyep]

Originally Posted by CraigS

Yeah Chris;

In isolation, its entirely possible that Mars once did have a thick atmosphere. Its also entirely possible it didn't, either. My point in raising the segment on the intact meteorite fragment, is only to point out that it is not immediately obvious from this alone, that the planet once had more of an atmosphere. I'd have to work out what the minimum impact velocity, energy etc, it would have to have, in order to accept it as evidence. I'm not saying its not evidence, either. If its not intuitive, then I'd expect more information to support the inference. There are heaps of variables in this (eg: Mars' gravity is one third of Earth's, etc, etc .. which raises an immediate questions, for me).

So why make a point of it if your not going to explain further ?

Venus has a very weak planetary magnetic field (and is not due to the iron core dynamo effect), but has heaps of atmosphere. Its closer to the Sun, so why hasn't it been stripped of its atmosphere ? (If the magnetic field is the only reason ?)

Venus has no plate tectonics, and they think this is a possible reason for it not losing its internal heat, and is the basis of a current a hypothesis for its lack of a dynamo type magnetic field. The atmosphere is extremely dense, and thus has more mass per unit volume. Gravity plays a role in keeping it there.

None of these points were raised in the doco.

Frankly, I think content-wise, this episode could have been presented better.

Cheers

Agreed, it's a shame that he had to wittle it all down into a 1hr segment. One thing i notice is that he keeps re-hashing his thoughts which is a little annoying, like "seconds from disaster"
Anyways, next week's epi will be interesting!