Samples of algae that were exposed for almost a year and a half to the harsh conditions of space on the outside of the International Space Station, returned to Earth still alive. Their survival raises hopes for finding life on Mars, may provide food and oxygen for Mars explorers, and could reopen a debate about how life may have come to Earth.

The samples were flown on an international European large scale project called Biology and Mars Experiment (BIOMEX), which is designed to study how living organisms can survive the rigours of space, and the hostile surface of Mars.

Samples of green algae from Svalbard, a Norwegian archipelago, and a blue-green algae from Antarctica, were placed in trays that were mounted on the outside of the international space station, where they were exposed to extreme heat and cold, radiation from the sun, and vacuum. The algae were chosen because they are well known for their ability to survive extreme cold and dryness in the polar regions of the Earth.

Since the samples were returned from space last July, scientists such as Jean-Pierre Paul de Vera at the German Aerospace Centre in Köln along with international partners, have been amazed at how well the tough little organisms survived in conditions that would kill a human in a matter of seconds. They are now looking for any changes that might have been made to their DNA because of the exposure.

Life in space

The fact that these living organisms survived exposure to empty space increases the chances that similar life forms could survive harsh conditions found at the surface of Mars, where temperatures are very low, and the thin carbon dioxide atmosphere provides almost no protection from deadly ultraviolet radiation from the sun. While the robotic explorers that have landed on the red planet have yet to find any signs of life, it could be hiding under rocks or in caves. And if not Mars, there are the ice moons of the giant planets, such as Europa and Enceladus, that might harbour this type of life.

Even if there is no native life on Mars, these algae could help future Mars colonists by providing breathable air and food.

Various specimens of green-alga strain grew new populations after gliding in low-Earth orbit for 450 days on the outside of the ISS. Only one specimen did not survive its space flight. (Thomas Leya/Fraunhofer IZI-BB)

Algae are just very tiny plants that take in carbon dioxide and release oxygen as they grow, an important function in a closed environment system like a Mars Colony. And if grown in large enough quantities, algae can be eaten, (but might need a little teriyaki sauce) or at least used as a food supplement.

The journey through space these algae took on the outside of the space station, supports the idea of Panspermia a belief that life forms spread around the universe by hitching rides on comets, asteroids and meteorites. The concept goes back to the ancient Greeks and has been supported by well-known scientists including Stephen Hawking.

If a planet that already had life on it was struck by an asteroid, some bits from the blast would be thrown out into space where they could eventually run into another planet. Microbes surviving the journey would then act as seeds to colonize the second planet. Several meteorites from Mars have been found on Earth, including one, ALH84001 that stunned the world in 1996 with what appeared to be the remains of a nanobacteria. Not everyone agrees with that assessment, so the jury is still out on that one.

Life travelling through space raises an interesting idea held by some believers of Panspermia; that the Earth was seeded with life from other worlds and in fact, we could all be Martians. It will take the discovery of life on Mars and a comparison of their DNA to ours to prove that, but in the meantime, this experiment raises the hope that life could be found hiding in bits of space debris, drifting among the stars like snowflakes waiting to rain down on habitable worlds.

It's an elegant idea with no proof yet, which is why we must keep searching for life in every imaginable niche.