MARS may have nearly as much ice trapped under volcanic debris as in its
northern polar cap, says a geologist.
Johann Helgason of Ekra Geological Consulting in Reykjavik, Iceland, was
studying Martian volcanoes. The largest, Olympus Mons, has unexpectedly steep
slopes. A smaller Martian volcano, Arsia Mons, has huge fans—possibly made
of lava—that extend a thousand kilometres to the south.
He says in Geology(vol 27, p 231) that the fans may have been formed
by “jökulhlaups”, eruptions that take place in Iceland under glacial ice.
These produce floods of meltwater, and Helgason says the fans of Arsia Mons look
like volcanic material transported by such meltwater.
Helgason thinks glaciers covered the volcanoes when Mars was wet. As lava
erupted, heat melted overlying ice, and a steep-sided volcano emerged. But some
surrounding ice did not melt. That ice could still lie under wind-blown dust,
and if so, volcanoes could hold nearly as much ice as the planet’s northern
Bruce Jakosky of the University of Colorado at Boulder says if Helgason is
right, this ice could account for some of the water on Mars that disappeared
early in its history. Surface features suggest there was once about 90 per cent
more water than today. But Jakosky is sceptical of the theory. “The biggest
problem is imagining a way to concentrate that much ice in one location,” he