h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Well, Mars is known for having huge sandstorms which appear at moments notice. One of the reasons why Mars expiditions often go bad. And I don´t think there is much reason to believe there are underground waterfilled caverns on Mars. As cool as that would be.

The Ocean of Omean.

Professor Percival Lowell was the eminent astronomer who 'saw' canals on Mars and promoted the notion of a civilised society using them for irrigation and transportation of water from the polar caps. He studied Mars on and off for fifteen years, drew maps as he perceived them and wrote books on the subject.
http://ltpwww.gsfc.nasa.gov/tharsis/canals.html

Many people did see them. However I do believe that Italian guy mentioned earlier was the first.

True. Sorry, but I didn't make it clear that I was responding to the comment
>..so there was never an implication of vast artificial waterways.<
in a previous post.

DK

Also on that link is a link from the homepage marked NEW! I don't understand the technical jargon but I think I understand the following -
...layer corresponds to soil with 50 wt % water ice and thickness much greater than 2 cm

so we are talking real Martian water here aren't we???

Traveller in Time trying to sterilise some soil
"Now only find a way to keep the solar radiation on an acceptable level and there might grow some complex chemicals . The atmosphere is really thin, does not block the radiation to a sustainable level. Even paint will loose its colour in days. "

I 'read' a scientific article (glanced in a paper on the railway station stand) which claimed that we're all Martians.
The reasoning was that Mars was habitable long before Earth due to it's quicker cooling. Then after life had become established on Mars, the story goes, a passing asteroids grazed the planet (photo showed a suitable scar on the red planet) captured some Martian lifeforms (bacteria etc.) and then dumped them on Earth.
Is Mars big enough to have had it's own atmosphere in the past?

Traveller in Time tasting the air
"There _is_ an atmoshpere on Mars. < A330823 >"

Thanks Traveller but what I suppose would really like to know is this:
In the past did Mars have a denser atmosphere than it has today?
Is the red planet of the size that it could once have had a dense atmosphere?
Is it of a size that a dense atmosphere could be held on to if one was created by some means - seeding the planet with plantlife that would produce such an atmosphere for instance?

It's a fascinating story which is presently unfolding largely due to the discoveries made by the two mars rovers and the global surveyor satellites. I'm no expert but I'll try to answer your question as best I can.

Current thinking is that Mars did have a denser atmosphere in its early life, although probably nothing so dense as the Earths, due to the lower gravity. Although it does seem to have been enough to provide sufficient pressure to support water in liquid form on the surface. The rovers have found plenty of evidence to support this in the form of sedimentary (layered) rocks and the famed 'blueberries' which are comparable to those found on Earth which only form in standing water.

The denser atmosphere permitted liquid water due to the higher atmospheric pressure but was eventually blown away by the solar wind. The atmosphere had originally been protected by the magnetic field generated by a fluid molten core in much the same way as the Earth is protected by its magnetic field which deflects the solar wind around our planet. As the core cooled and ceased movement, the magnetic field declined allowing the solar wind to impinge on, and 'blow away' the atmosphere. We already know that Mars's core has solidified from the evidence that the giant volcanos like Olympus Mons etc are the size that they are. The sheer weight of the cones could not have built up on a surface crust over a molten core, it would simply have subsided under its own weight.

It would therefore, I think, probably be impossible to create another atmosphere without providing protection from the solar wind.

Hope this helps
DK

That's very interesting about Olypmus Mons, Deke.

It seems on the face of it that we have 3 planets, Venus, Earth and Mars, in various stages of evolution. First Mars cools and gets a solid core, then in the middle Earth (now in the prime of life), and yet to come the juvenile Venus still shrouded in poisonous clouds.

If we can't seed Mars so that it gets an atmosphere it can hold on to is there any way then of speeding up things on Venus - i.e. changing the atmosphere into one suitable for life possibly by growing some kind of quick spreading plantlife. Or is that out of the question too?

I originally had the thought that we could sow some quick spreading greenstuff on Mars but from what you say we'd have to provide plastic covers to protect the fragile new atmosphere being created from seeping away into space.

This raises another question: Venus has lower gravity than Earth and takes a far stronger battering from the sun than Mars - and yet still has a much denser atmosphere. What gives?

Venus has a 'runaway greenhouse effect'. All the carbon which is locked up in limestone etc. on Earth (by life), has oxidised into CO2 on Venus. If the same thing happened here, atmospheric pressure would be approx 60 bars (1 bar now) and the temperature would be 2-300C.

I think that has to do with what gasses the atmosphere is made out of. You could give Mars a dense atmosphere, if you used heavy gasses. But then it wouldn´t be breathable for humans.

If you wanted to terraform Venus, you might be able to start out by seeding it with blue green algae. It would take a thousands or so years though. At least those are the proposals I have heard. However I don´t think you can consider Venus to be juvenile in anyway, it just had had a different development. It won´t become Earth-like by itself even if given another billion years.

This is an area we're going to have to research and develop if we want to colonise the solar system

before we do any research on colonizing the solar system, we need to find a way to travel between planets. We are so far away from being able to do that...

In travelling between earth and Mars, a photon of gamma radiation and/or ionized particle will travel across the entire length of every cell in your body. This is extremely likely to induce cancer, rapidly.

>>"We already know that Mars's core has solidified from the evidence that the giant volcanos like Olympus Mons etc are the size that they are. The sheer weight of the cones could not have built up on a surface crust over a molten core, it would simply have subsided under its own weight."

I'm a bit puzzled - if the planet *was* already solid, where would the molten material come from to build volcanoes?

You've also got to remember that the gravity of Mars is much lower than that of the earth - therefore much larger mountains _could_ exist without collapsing under their own weight (they don't actually weigh as much!)

>if the planet *was* already solid, where would the molten material come from to build volcanoes?<

I think we are referring to a simultaneous process of cooling and volcanism. The planet was not already solid, but being smaller it did cool more quickly than the Earth. While it was cooling the outer crust thickened first providing the strength to support the successive layering of magma over a considerable period of time.

>You've also got to remember that the gravity of Mars is much lower than that of the earth - therefore much larger mountains _could_ exist without collapsing under their own weight (they don't actually weigh as much!)<

Yes, but you also have to consider that this is not just a large volcano. It dwarfs anything on Earth and is the largest known volcano in the solar system. At 24 kilometres high it is three times higher than Everest, and some 600 kilometres across the base. The sheer bulk of such a structure, which is reckoned to be 100 times the volume of its largest equivalent on Earth, could not have occurred on a thin crust above a fluid mantle even with a reduced gravity.