Earth’s Sibling

Looking up into the western sky just after sunset, a bright non-twinkling star shines, then turns progressively pinker as the evening wears on: our neighboring planet, Mars. As of Friday, when the Pathfinder spacecraft, encased in giant air bags, bounced down to the surface of the Red Planet, Mars is also looking back at Earth--a pale blue dot on its horizon.

By Sunday, Pathfinder had sent out its one-foot-high rover, Sojourner, to explore the planet--the first time a roving vehicle has ever left its tracks in the Martian dust. Now Sojourner, too, is taking pictures: of its mother ship, Pathfinder, with its now-deflated air bags, and of various rocks and soil. It is also conducting the first-ever chemical analysis of a Martian rock. According to the first results, at least one Martian rock, called Barnacle Bill, looks more like Earth than scientists had expected. That’s not surprising, perhaps, for a close sibling like Mars.

But in many ways, the fourth rock from the sun is truly otherworldly. While scientists believe it once had vast oceans, it is now parched, barren, rusting slowly, with a highly reactive surface that would destroy any possible forms of life.

What happened to the water? Was there ever life on Mars? Could there still be life buried deep inside the surface?

The success of the rover named after civil war abolitionist Sojourner Truth will help make possible future Mars missions that can answer these juicy questions.