Space/Science — HabitableZone

Space/Science » in reply to as the Sun's activity declined...

thanks for the reminder
Adam — (archived)

Hi Nick

Sorry for my lack of proper decorum in these discussions. The "Solar Wind will erode Mars' atmosphere" thing is a truism that I'm sick of, but that's no excuse for getting confrontational.

As for the Wind's evolution, it was still enhanced long after the T-Tauri phase AFAIK - at least it's assumed to have been so enhanced in every paper I've read on the erosion of Mars' atmosphere. The present day Solar Wind is a shadow of its former self.

Thus my basic point remains - the incident energy from the Wind is very low, less than the incident solar radiation, and insufficient to erode the present atmosphere except on a gigayear timescale. A simple BOTE calculation is enough to see that for oneself. Repeating a truism belies a lack of critical thought IMO.

One question I do have is just how much cosmic ray protection the Earth's magnetic field provides. I hear various idiotic claims of how much worse it would be without the dipolar field, but there's no evidence for any kind of biosphere upset during low-field epochs in Earth's history. Seems like another "urban scientific myth" or truism, but I'd like to see decent numbers. As far as I can tell the Solar Wind would be semi-deflected by the Earth's ionosphere if the field failed - much like Venus or even Mars. The Galactic cosmic-rays would interact directly - but the high energy ones do anyway. The uncertain thing is the lower energy range, where most of the GCR spectrum is. Do you know?

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