With uncertainty around life on Mars, human visits present an ethical dilemma

The first step by a human on the surface of Mars will inevitably transfer Earthly microbes onto Martian soil. Scientists are increasingly concerned with what the implications of contaminating another planet will be.

A recent study, published this month in the journal Microbiome, analyzed the clean rooms at the Kennedy Space Center, where Mars landers are sterilized before launch. The team found 26 species of novel bacteria that could potentially survive the harsh environment of space.

These organisms contain genes that enhance DNA repair, detoxification of harmful molecules, and enhance metabolism, all of which makes them more hardy.

NASA goes to great lengths to ensure any spacecraft that departs for Mars is sterilized in these ultra-clean rooms and sealed in capsules before launch to prevent cross-contamination between two planets.

We don't know whether any of these microbes actually made it to Mars because we have no way of examining the spacecraft while they are on the Red Planet.

The chances of microbes surviving the vacuum of space, extreme temperatures, along with solar and cosmic radiation are slim, however there was a case where Earth microbes did seem to survive for years on the moon.

In 1969, the crew of Apollo 12 landed close to a robotic probe called Surveyor 3 which had arrived on the lunar surface three years earlier. The astronauts removed a television camera, electrical cables and a sample scoop which were returned to Earth for study on the long term effects of exposure to space.

To everyone's surprise, a common bacteria, Streptococcus mitis, was found inside the camera lens. This harmless organism, normally found in the mouth and throat of humans, was thought to have been on the spacecraft before launch because Surveyor was not sterilized.

A later study done by NASA in 1998 suggested the bacteria could have come from contamination due to poor procedures after the lens was returned to Earth. But there is still the possibility that microbes could survive in space.

Sterilizing a robotic spacecraft to prevent contamination is one thing, but sterilizing human beings is impossible. We are substantially made of bacteria, covered in microbes from head to toe and internally, constantly shedding them with dead skin and other detritus. And those organisms will travel with us to Mars.

New species of bacteria have been found inside China's Tiangong-1 space station and astronauts on the International Space Station are constantly cleaning the walls to prevent the buildup of microbes in that sealed environment. This is evidence that bacteria can survive the higher radiation environment of a space habitat.

That means any human boot that touches the Martian soil will bring with it organisms from inside the spacecraft or colony. Whether those bugs could survive long in the Martian environment is to be determined, but the more serious issue is what they would do to any indigenous organisms that could already be living on Mars.

Curiosity, one of the rovers currently driving around on the Red Planet, has been collecting soil samples from different areas and sealing them in tubes to be collected and returned to Earth by a future sample return mission. The idea is to look for signs of current life or fossils of past life using the powerful tools in Earth laboratories.

But NASA is proposing cancelling the sample return, so we may not know for some time whether microbes exist in Martian soil.

Mars shows signs of a warm and wet past, where the planet was once covered with lakes, rivers and oceans. This was during a time, roughly three billion years ago, when life was emerging on Earth. So far, no signs of life have been found on Mars, but we have only been looking on the surface, not underground where water might exist.

Still, there is talk of sending people to Mars, even establishing a Mars colony. But is that wise before we determine whether the planet has life or not?

In the classic science fiction story, War of the Worlds by H.G. Wells, Martians come to Earth with invincible machines that wreak havoc on cities. Our most powerful weapons are useless against their incredible power. But eventually, the invaders are taken down by the tiniest creature, the common cold, for which they had no resistance.

In real life, the tables are turned. We are the invaders from Earth who are bringing our machines and alien organisms. If we do discover Martian life, should we go there at all?