“Something big smacked into Mars…”

“…and stripped half the crust off the planet.” That’s a new theory about the Red Planet reported in Science News and elsewhere.

The problem: The north half of Mars is very smooth, while the southern half is covered in craters and craggy plateaus. The proposed solution is the title of this post.

By mapping surface elevations, crustal thickness and variations in gravitational pull, MIT’s Jeffrey Andrews-Hanna and colleagues uncovered a gigantic scar – a pockmark covering about 40 percent of the planet’s surface. “Finding this elliptical boundary is a smoking gun,” Andrews-Hanna said.

I suppose it’s too early yet to say if an impact like this would be enough to zap a planet’s store of liquid water (and its technologically advanced alien civilization). But it sure is fun to speculate.

NB: In that same issue of Science News, there’s a rather nice column by Dudley Herschbach called “Seeding liberal arts courses with science parables,” about the stories of scientific discovery. If anyone ever wonders why students learn calculus, the bit about Jefferson’s plow is instructive.