SUMMARY: Photographs taken by the European Space Agency's Mars Express spacecraft seem to indicate that there still could be active volcanism on the Red Planet. The spacecraft took detailed observations of five Martian volcanoes, and found that some had erupted as recently as 4 million years ago. Although this is ancient in human terms, it means that Mars is still probably geologically active. This is very important to biologists, because it means that there could be geothermic vents with heat and liquid water - havens for microbial life.

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Interesting! raises a few question on our understanding of internal structure of a planet.

What keeps the interior of a planet molten? Is the core of Mars Molten but no tectonic plates moving? Or has the core cooled off too?

What role has the moon to play in plate tectonics? Does the moon simply raise the water level of the sea or the land as well? Does it churn the plates too? Phobos cannot possibly do that.

If we suddenly loose our moon will the water recede to some pockets deep inside?

While Earth and Mars were possibly born alike but our moon saved us and Mars has gone almost dead for want of a big enough moon.

I was under the impression that Mars does not have as molten an interior like Earth's. This impression was based on the fact that Mars does not have a global electromagnetic field. The lack of such a field has allowed the solar wind to essentially rip away Mars's atmosphere and any surface liquid water. Does this mean that Mars could have a simliar interior to Earth's, and if so why doesn't it produce an EM field?

I won't respond to alot of the comments just made. But the first question is worth addressing. The lack of a magnetic field at this point is the best clue about its interior. The Earth's magnetic field is thought to be generated by a liquid core rotating about a solid inner core. Whether the core is made up of uranium or solid nickel/iron is still debated. The convection of liquid metal about the core generates the field. The fact that there is no magnetic field on Mars tells us that there is no liquid outre core and probably no liquid inner core of any significance. But this does not preclude pockets of magma from forming in the mantle as radiaoactive elemets decay over time. There may also be hot spots of magma still rising from the inner mantle. Considering that there is a tendency for decay of elements in the mantle generating heat, I am not sure that any planet will ever be "geologically dead," but rather there would be a trend towards less and less magma eruptions over time.

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I'll try to provide a general answer to these questions.

1) The short answer is probably heat from radiated elements left over from the formation of the planets, combined with some left over heat from the accretion procees which formed the planets. In larger planets (like Earth) there may also be some degree of heat generation as a result of convection. Classical planetary formation models assign the biggest cause to radiation.

2) This is unknown for sure. It would seem that there may still be some degree of melt in the Martian core, but it is buried beneath alot of solidified mantle. On Earth, tectonics are driven by the melted mantle, not the core.

There is some evidence of tectonic activity on Mars, but the evidence is scarce and seems to be very old, about 3.5 billion years old. This would not affect intrusions of magma from the lower core/mantle boundry, nor from pockets of heated mantle arising from radioactive decay.

3) Very little. The Earth is much more massive than the moon, and the plate activity arises from the convecting mantle, not tidal bulging. The moon's gravity might contribute some heat to the mantle as a result of tidal bulging, but it is not a significant contribution. It does not churn the plates at all.

Nope, it is WAY too small to have such an effect on Mars.

Nope, although we would have much smaller tides. There would still be tides by the way, arising from the sun's gravity. There is no place for the water to recede to.

6) Well no actually. Mars is geologically inactive because it is so small as compared to the Earth. This has caused a number of events to transpire to remove its atmosphere, including sputtering (losing atmoshere to the solar wind) Jean's Escape (losing atmospheric elements that have been excited beyond Mars' escape velocity) and impact induce atmospheric erosion (where the atmosphere is "lifted" by an impact and is lost because Mars' smaller mass can't recapture it).

7) Not at all. While Mar's may have some degree of molten mantle and/or core, it most assuredly is nothing like the Earth molten interior. Again, there may be pockets of molten magma or maybe intrusions of magma from the deep core, but these are transient events and do not lead to the conclusion the Martian mantle is melted to any degree.

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All civilizations become either spacefaring or extinct.~ Carl Sagan ~

Humanity must rise above the Earth, to the top of the atmosphere and beyond, for only then will we fully understand the world in which we live.~Socrates, 500 B.C. ~

Let every man judge according to his own standards, by what he has himself read, not by what others tell him. ~Albert Einstein~

How long until geologists can predict the next period of martian geological activity?

Thanks Duane, Have a Meery Christmas!

It is not known how long it will be till they can predict the next period of Martiological activity. Personally, I think that the Martian Volcanos and the Valles Marinaris are artifacts from a large body colliding with Mars on the other side of the planet relatively recently, and are not a sign of long held interior heat in the planet.

Note that this is NOT a well established theory, but is merely me trying to apply common sense to where these Volcanos and giant canyon could have come from so recently with no obvious sign of similar earlier activity.

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oh yes, thanks for asking that, I had meant to add that to my earlier post. The way for us to find out is to setup a series of sizemographs around the planet and listen to what happens to sound waves that get transmitted through the planet. It is similar to taking an x-ray or CT scan of the planet. That is how we know what we know about Earth's interior. Of course setting up such a system would take considerable time, effort, and money. It is something that will need to be done when we are nearly ready to establish a permanent prescence there. It could be done sooner, of course. I am not aware of any way to get such information by satellite, or I a msure it would have been done by now.

__________________
Quid hoc ad aeternitatum
The conversion of complex and abstract ideas into simple and concrete ones is the essential function of teacher of a body of knowledge.

I would think this to be very unlikely. The Tharsis region shows evidence of several different periods of eruption, building the area over the course of many millions of years. The Valles Marinaris is also an indication of the solidification of the Martian mantle. The area seems to reflect the shrinkage of the Martian crust as the mantle cooled to the point where it solidified.

An impact event would be obvious, even a very large one. No such evidence exits on Mars, suggesting such an event did not happen.

I agree Greg, seismographs might give a picture of the interior, assuming that there are any Mars quakes. The problem would be if there are no quakes, or of they are very small, you wouldn't get any readings.

__________________
All civilizations become either spacefaring or extinct.~ Carl Sagan ~

Humanity must rise above the Earth, to the top of the atmosphere and beyond, for only then will we fully understand the world in which we live.~Socrates, 500 B.C. ~

Let every man judge according to his own standards, by what he has himself read, not by what others tell him. ~Albert Einstein~

I think the Hellas Basin is an obvious such place.

That being said, it will only take a small amount of sampling and radioisotope dating to prove this idea right or wrong.

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Sorry, not big enough. While Hellas is big, you are talking about an impact large enough to liquify the mantle on the opposite side of the planet such that the largest volcanoes in the solar system arose. Such a large impact would leave many other signs, none of which exist on Mars.

__________________
All civilizations become either spacefaring or extinct.~ Carl Sagan ~

Humanity must rise above the Earth, to the top of the atmosphere and beyond, for only then will we fully understand the world in which we live.~Socrates, 500 B.C. ~

Let every man judge according to his own standards, by what he has himself read, not by what others tell him. ~Albert Einstein~

Perhaps so, but this really is a puzzle, since it seems pretty unlikely that Mars would have had heat from radio-isotope decay that only revealed itself as volcanos in one isolated part of the planet, that only appeared recently.

I make no claim that my model must be correct, but the model you describe has some big problems too.

Sadly, the Mars 2009 rovers aren't likely to measure anything that can tell us more.

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Forming opinions as we speak

Actually, the ancients describe another star passing by Mars and causing all kinds of havoc, turning a once luscious planet into a barren wasteland.

Not that I'm trying to apply religion to this string...but it's something to think about in relation to Anton's claim.

The thing is, the volcanos and Valles Marinarus seem to be closely linked, with the entire Tharsis plateau sitting directly beside the Valles. The Tharsis Plateau has significant layering evident, suggesting that the area was built up as a result of many eruption events covering a period of eons.

With the incredible weight of the Tharsis Plateau combined with the early solidification of the mantle and resultant shinkage of the Martian lithosphere, you would almost think such a crack must appear somewhere on the planet.

I also see no issue with radioactive decay giving rise to heat in the interior of the planet, nor do I have a problem with multiple eruption events following essentially the same path through the solidified, or at least plastisized, mantle. It is the same with water--once liquid water finds a path through something, even minute cracks in rocks, it will continue to follow that path each time the water reappears. I see no difference with the Martian interior, especially if the molten magma is continually heated by radioactive decay. It would be similar to the geysers in Yellowstone. The heated magma slowly builds pressure as a result of expansion until is finally pushes its way to the surface to relieve the pressure.

I don't see a catastrophic event as having the necessary staying power to create these multiple layers of lava flows as seem evident on images of the area. This was not a sudeen event, it was one that lasted for many many years.

__________________
All civilizations become either spacefaring or extinct.~ Carl Sagan ~

Humanity must rise above the Earth, to the top of the atmosphere and beyond, for only then will we fully understand the world in which we live.~Socrates, 500 B.C. ~

Let every man judge according to his own standards, by what he has himself read, not by what others tell him. ~Albert Einstein~