Mars question

[Jeters_Boy]

According to this recent article,

http://www.dailymail.co.uk/sciencet...-Great-northern-ocean-covered-Red-Planet.html

the surface of Mars was once partially covered with water. My question is, what has caused the temperature of Mars to drop to what it is today?

 

[a_lost_packet_]

According to this recent article,

http://www.dailymail.co.uk/sciencet...-Great-northern-ocean-covered-Red-Planet.html

the surface of Mars was once partially covered with water. My question is, what has caused the temperature of Mars to drop to what it is today?

Well, for one thing, Mars' gravity isn't strong enough to sustain much of an atmosphere for very long. It's hypothesized that whatever atmosphere Mars has had in the past, it leaked away over time.

Also, Mars doesn't have much of a magnetic field to help establish some sort of protection from damaging particles coming from the Sun. Earth, on the other hand, has a strong magnetic field generated, most likely, by a "dynamo" effect arising from its hot, active core. Mars' core seems to be no longer as active as it once may have been and whatever dynamo effect it could have had early in its development has long since wound down.

Without an atmosphere, there's no insulating blanket. Current events revolve around a discussion of Earth's "Global Climate Change" and that is directly dependent upon our atmosphere. Our atmosphere provides a "greenhouse" effect that traps solar radiation, resulting in retained heat. Mars' existing atmosphere isn't hefty enough to provide a means to trap as much warmth like Earth's own atmosphere.

Air pressure is... air pressure. In other words, an atmosphere has some heft to it, some "weight." That provides "air pressure" at the surface. Without it, a lot of things would be more inclined to be spread out.. most notably, subjected to the vacuum of space. If liquid water such as would exist at sea level on Earth is subjected to that, it "boils off" as dissolved gases are released.

An interesting vid of water "boiling" in a vacuum. This is what would happen with the absence of an atmosphere.

[youtube]http://www.youtube.com/watch?v=9q5gEZGoBnk[/youtube]

Water ice avoids the whole "liquid water" phase entirely by "sublimation" when exposed to lower atmospheric pressures. Here, we can see what is, apparently, water ice undergoing sublimation on Mars' surface after being disturbed by the Phoenix Lander:

Bright Chunks At Phoenix Lander's Mars Site Must Have Been Ice

A lot of water ice seems to lie under Mars' surface, remnants of Mars' past.

Found it! Ice on Mars

 

[3488]

Excellent post & answer A-L-P.

Really there's not much else to be said.

I will mention the average solar insolance at Mars is only 44% as at Earth (508 watts per square metre, as againt Earth's 1,320 p s m), so if we where to dim the sun by 56%, to match that at Mars, it would be pretty parky here too (the Earth probably would not get as cold as Mars's average global temps, due to denser atmosphere).

As A-L-P correctly said, Mars almost certainly had a much denser atmosphere, being maintained by the huge volcanoes & also protected by a global magnetosphere.

Volcanism waned, the Martian core solidified enough to stop convecting (may have been dual layered at one point before it cooled enough & fused into a single, non convecting core), magnetosphere collapsed, solar wind started stripping the atmosphere away, leaving behind what we see today.

Andrew Brown.

 

[coogs]

Where has the water gone on mars?

This question was asked recently by space.com

What would happen if the earth suddenly cooled.?

Would the interior suddenly shrink creating vast interior voids capable of accommodating the oceans found on the surface.

I'll ask another question! What if Mars interior is still warm enough to keep its possible underground oceans in liquid form.?

We would have vast underground oceans filled with possible life which might explain the cycle of methane entering & exiting the atmosphere.

I'll bet on vast underground oceans!!!

 

[a_lost_packet_]

..I will mention the average solar insolance at Mars is only 44% as at Earth (508 watts per square metre, as againt Earth's 1,320 p s m), so if we where to dim the sun by 56%, to match that at Mars, it would be pretty parky here too (the Earth probably would not get as cold as Mars's average global temps, due to denser atmosphere).

Excellent point. I knew someone would eventually cover that aspect so, I left it to more capable enthusiasts.

As A-L-P correctly said, Mars almost certainly had a much denser atmosphere, being maintained by the huge volcanoes & also protected by a global magnetosphere.

Volcanism waned, the Martian core solidified enough to stop convecting (may have been dual layered at one point before it cooled enough & fused into a single, non convecting core), magnetosphere collapsed, solar wind started stripping the atmosphere away, leaving behind what we see today.

Andrew Brown.

Excellent point - Martian volcanism was pretty rampant early in its history. It also possesses the largest volcano in the solar system, Olympus Mons. But, today, there's little or no evidence of active volcanism on Mars that I know of.

A neat comparison of Olympus Mons to Mt. Everest and Mauna Kea.

 

[3488]

Thanks A-L-P for that graphic. It really does show how tall Olympus Mons is.

[youtube]http://www.youtube.com/watch?v=1BPNVtCgAbk[/youtube]

Hourglass crater
[youtube]http://www.youtube.com/watch?v=fiV5ieCdBNc[/youtube]

Vallis Marineris.
[youtube]http://www.youtube.com/watch?v=s3KiGqL_lH0[/youtube]

Andrew Brown.