Dire warnings have been sounded\u2014the members of The Bulletin of Atomic Scientists' Science and Security Board have reset the Doomsday Clock, an analogy for the threat of future global catastrophe that could wipe out humans, to two and a half minutes from midnight (or the global catastrophic event). Initially, the clock represented the threat of a catastrophic man-made nuclear event; now, it covers all sorts of factors that could imperil human existence, from climate change to developments in life sciences and technology that could do irremediable harm. Ace physicist Stephen Hawking gives humanity 1,000 years on Earth before it is wiped out\u2014and 100 years to get out and colonise other planets. Such talk, and, of course, the quintessential human yearning for exploration and discovery, has fuelled the search for alternative homes. Every now and then, reports of Earth-like conditions in our solar system and Earth-like planets elsewhere in the galaxy send frissons of excitement down humanity's spine. But, when it comes to colonising extra-Earth bodies, nowhere do we turn to with more hope than Mars. Private companies, if Mars One and SpaceX are any indication, are getting just as keen as government-run space agencies when it comes to exploring the planet. In fact, SpaceX founder Elon Musk is very bullish on Mars as far as his vision of making human beings a multi-planetary species is concerned. Just last month, in a non-academic paper published in a journal called New Space, Musk shared details of his vision. He hopes to put 1 million people on the Red Planet in the next 40-100 years\u2014note how this coincides with Hawking's warning\u2014to create a \u201cback-up drive\u201d for human civilisation. But could it be that he is seeing silver linings where there are only clouds? Mars is a cold desert\u2014in the peak of summer, standing on its equator, you will experience freezing cold (~20oC). There is almost no atmosphere to speak of\u2014the atmospheric pressure is 0.07% of Earth\u2019s\u2014and whatever little there is, is an unbreathable mix of CO2, argon and nitrogen. But, theoretically, these problems can be resolved. The University of California San Diego says that creating reasonable atmospheric pressure would need heating the planet to evaporate CO2 out of the planet's polar caps. And reliance on the gas from a hypothetical reservoir trapped beneath the Martian regolith\u2014the unconsolidated surface covering the bed-rock. The next step would be to introduce certain extremophile bacteria from the Earth on the Martian surface to tweak its atmosphere to resemble that of Earth. The cyanobacterium Chroococcidiopsis would be a good candidate for this. (For those interested in learning more about extremophiles, there is enough literature on the Danakil Depression in Ethiopia, the most inhospitable region on Earth.) The extremophile bacteria could then convert the CO2 into oxygen and sequester the carbon. So far, so good. You may also like to watch: The problem is that the Martian surface is covered with hyperoxides that will rapidly burn any organic matter upon contact. Organisms that can withstand such hyperoxides remain yet undiscovered on Earth, and the probability that there are such creatures is next to nil. Bioengineering acidophiles could help, but we are years away from this. All this apart, a new study has found that oxidising perchlorates (ClO4- salts) that are common on the Martian surface kill bacteria within minutes\u2014researchers at the University of Edinburgh simulated Martian perchlorate and UV light (that activates perchlorates, as does heat) concentrations and found that it killed Bacillus subtilis, a basic life form from Earth. This means any attempt to heat the planet to create a conducive atmosphere could trigger greater perchlorate action. And given how perchlorates are widely used in propellants and explosives\u2014making them common in aerospace travel and modifying topograhy through controlled blasts\u2014attempts to terraform Mars could just add to their concentration there. Just how deadly a cocktail of toxic surface and thin atmosphere Mars offers should be clear from the Edinburgh research. Bacteria died twice as fast from perchlorate + UV rays than from UV rays alone (thin atmosphere means greater concentration of UV rays). And when hydrogen peroxide and rust, common Mars natives, were introduced to the mix, bacteria died 11 times faster. All of this would suggest that the Red Planet is more inhospitable than thought to be so far. So, unless Musk wants colonisers to live out hundreds of years\u2014that is, if terra-forming efforts surpass present capacity by gazillion times\u2014in pods that simulate Earth-like condition, an actual colonisation of Mars may be impossible. What's worse, at the end of it all, Mars is too small a planet for its gravity to hold on to the kind of atmosphere humans require sustainably. Which means living on Mars would be just biding time from one crisis to the next.