Fire Still in Mars' Belly?

Scientists studying images of the huge volcano complex on Mars think it's possible the volcanoes may be dormant, not extinct.

The images taken by both NASA and ESA craft orbiting the planet suggest lava could have flowed down the flanks of the volcanoes within the last two million years. That sounds like quite a long time, but in geologic terms it leaves open the possibility of future activity.

Scientists are also discussing a new theory. Up till now, they have used the shield volcanoes in Hawaii as models of Mars' major volcanoes. In Hawaii, the Earth's crust has moved over a so-called "hot spot" that powered volcanoes and created the Hawaiian chain. On Mars, the situation might be exactly the opposite. The Martian crust may be stable, but a plume of magma may be moving around underneath. When the plume comes in contact with a weakness, the magma might break through.

How a possibly active Mars might affect plans for human exploration is unclear. Planets and people operate on vastly different time scales, however. The odds that dormant volcanoes would come back to fiery glory just as humans reach Mars must be long indeed.