Humans have walked on only two worlds in the solar system — Earth and its moon. But it’s looking more certain that Mars may be the next member of this exclusive club. Along with NASA, private companies like SpaceX and Mars One are itching to put boots on the Red Planet. Human exploration could certainly improve the science performed on Mars, but our arrival could also have important implications in the hunt for life.
Whether or not life ever managed to evolve on Earth’s red neighbor remains an open question. Conditions on Mars don’t support large creatures, but microscopic life-forms may have once thrived in the planet’s oceans. They may even survive today in the sparse pockets of water on and below the Martian surface. If so, it’s possible they could be similar to Earth’s life-forms: Life may have managed to jump from one world to the other by riding on rocks flung off their surfaces by asteroids.
The alternative would be no less significant. If Mars is barren, and researchers find that life evolved only on a single planet in the solar system, it reveals how difficult it is for living organisms to arise in the first place, with implications for the rest of the universe.
But there’s an automatic difficulty in clearing up the mystery of “life on Mars,” an inherent catch-22: Any astronauts touching down to investigate life could contaminate the area with their own microbes, making it impossible to know the truth. NASA has long had protocols in place to limit such contaminations, but with the increased pace of private efforts, and the growing likelihood that actual humans may reach Mars, those standards might have to change.
