For decades, the popular scientific belief has been that life couldn't exist on Mars: the planet is just too harsh to support life. But then scientists started finding microbes living in extreme conditions on planet Earth -- conditions like extreme heat (boiling water), extreme cold, extreme pressures, extreme pH, lack of sunlight, and so on. The organisms that live in these conditions are called extremophiles, and their presence on Earth has scientists thinking twice about what sort of life is possible on Mars.
Without question, Mars offers opportunities for life that are less extreme than the Earthly extremes named above. And if microorganisms can survive in these conditions on planet Earth, there's no reason to believe they couldn't live on Mars. After all, life was brought to Earth from comets and meteorites, and Mars has been hit by the same sort of rocks carrying the same catalysts for life.
In fact, you have to really deviate from scientific thinking if you're going to conclude there's no life on Mars. The existence of life on Mars is a near-certainty, and I've said that publicly for years and will keep saying it until NASA finally admits it. The only reason NASA hasn't already announced life on Mars, I've theorized, is that the news would simply be too much for the masses to handle. It could upset conservative religious folks, for one, and even cause political upheavals. So for now, they're keeping the news under wraps until the world is ready to hear it.
But that's just a theory. Perhaps the agency is waiting until they have a larger body of proof about life on Mars. After all, when you make an announcement like that, you want to be able to back it up with indisputable evidence.
As NASA's two robotic rovers wind down their mission on Mars, scientists searching for possible signs of Martian life are now training their attention on a landscape much closer to home: the remote regions of planet Earth.
A wave of findings in recent years has shown that some tiny organisms can survive further below the Earth's surface than scientists had long thought, as well as in sulfur pools, boiling water, and other harsh environments.
Many scientists now believe that if life exists in the unforgiving conditions on Mars, the most likely candidates would be these kinds of microorganisms, known as extremophiles.