Last November, NASA scientists rehashed an old claim – no, not that the polar cap will disappear in four years – but that there is evidence of life on Mars on an asteroid discovered in 1984. Further clarification has been offered over the weekend. Behind all the hullaballoo over how these “biomorphs” were found, one inconvenient fact is ignored: they are too small to be living things.

Back in the nineties, “nanobacteria” were theoretical self-replicating calcifying particles believed to be necessary to account for certain bacterial functions. At the time the first “life on Mars” announcement was made in 1996, it was still believed that nanobacteria could be true lifeforms. The shape and chemical composition of formations on the ALH84001 asteroid were similar to putatively identified nanobacteria of Earth. However, a geological process was suggested to explain the formations, so the nanobacterial explanation of the asteroid subsided in public discourse.

It should be emphasized that “nanobacteria”, contrary to their name, are not bacteria, or even lifeforms at all. At 20-100 nm across, they are too small to have nucleic acids (DNA or RNA) or conduct even the most basic bacterial biochemistry. The smallest known bacterium, by contrast, is well over 300 nm across, and it is physically impossible for a true lifeform (with nucleic acid, ribosome, protein) to be smaller than 200 nm. All known nanobacteria have no organelles of any sort; they are just globules of carbonate compounds. To call them lifeforms is a serious abuse of language.

The death knell for nanobacteria was sounded in a series of papers in 2007, 2008 , and 2009 proving that putative “nanobacteria” were just carbonate nanoparticles. They may replicate, as do many crystals and polymers, but they have no nutritive or genetic functions, so they can hardly be considered life unless we lower the bar considerably.

Ironically, although the star of nanobacteria had by then faded, in 2009 NASA published evidence that the observed iron sulfide and iron oxide grains on the 1984 asteroid were not the result of a geological process, but were likely caused by nanobacteria activity. The NASA scientists, followed by the press, proclaimed this as evidence of life on Mars, even though by now it was understood that nanobacteria are not lifeforms in any standard sense of the term. Some reports even referred to nanobacteria as tiny bacteria, as if the only difference were one of size, when in fact the inaptly named “nanobacteria” are not bacteria at all. The lay reader could be excused for not knowing that this “life from Mars” is too small and structureless to have DNA or RNA or any internal metabolism.

What the new evidence really shows at most is that the grains on the Mars asteroid really were produced by nanobacteria and not by some other geological process, so the globule formations on the asteroid are likely to be fossil nanobacteria. This identification however does not have any bearing on the microbiological question of whether nanobacteria themselves are living things, a question that is increasingly being answered in the negative as the crystallization processes that form these nanoparticles become better understood.

It is certainly possible that so-called nanobacteria are a precursor to life, just as water, as far as we know, is a necessary condition for life. Yet a necessary condition is not a sufficient condition, so the presence of carbonate nanoparticles is a far cry from proof that Mars ever developed life at some point, just as the presence of water is no proof that Mars was ever habitable. I may need wood to build a house, but the presence of wood in a forest is no proof that there were ever houses there. Such is the vast gap between nanoparticles and the simplest bacterium. Abiogenesis, it should be noted, remains pure speculation, without any empirical verification or well-defined theoretical mechanism.

The real reason to tart up the evidence for life on Mars is to justify the boondoggle of our manned space program, which is still struggling to develop a vehicle to return to the Moon. There is practically no real science that can be done with manned missions that cannot be done with robots, except studies on the effects of microgravity on humans. The idea that there might be other life out there is what gives the whole concept of manned space exploration some credible purpose. Otherwise, we’re just exploring rocks and gas giants that could just as easily be observed by probes.

While one should never say never, the Fermi paradox is looking as strong as ever, and we may at some point be forced to admit that life is so rare in the universe that we are unlikely to encounter it in any form for thousands of years, if ever. Our efforts might be better spent, then, in tending to our own world, while others perhaps tend to theirs.

Update – 29 Apr 2010

In a case of “be careful what you wish for,” the Obama administration has effectively killed the U.S. manned space program, canceling the Constellation program without any alternative, while the shuttles will be grounded after this year. Responding to a negative backlash, the politically adroit president backpedaled, making a vague promise (not a concrete mission) of an eventual trip to Mars, and partially reactivating the Orion capsule program as an unmanned payload and escape capsule. These are purely face-saving measures. The President does not even have to decide on a heavy lift design until 2015, which means there will likely be at least a full decade when the U.S. does not have manned space flight capability, assuming the program isn’t postponed or killed along the way. In the meantime, we can expect an exodus of aerospace talent to Europe, Russia and China.

Taking a page from George W. Bush, Obama has sought cover from the private sector, promising that companies will be able to take astronauts into low earth orbit for ISS missions. In fact, they are nowhere near such capability. There is a vast technological gap between launching manned and unmanned spacecraft, and between orbital and suborbital flights. Only one company, SpaceX, has successfully achieved suborbital manned space flight. Their “spacecraft” are actually rocket-powered aircraft that exceed Mach 3. It would require more than 60 times the energy to reach orbital speed, not to mention the formidable engineering difficulties of space navigation, docking, life support, and re-entry. For every SpaceX, there are a dozen failed space ventures, yet this is supposed to be our most cost-effective means of returning to LEO.

Make no mistake: Obama is not a fool. He simply is not terribly interested in the manned space program, as is proved by his actions. Nor can he expect sound advice from his space policy advisor Lori Garver, a career policy wonk with zero engineering experience and a fetish for “climate change” pseudoscience. It is true that much good science can be done more cost-effectively with unmanned probes, as I myself have argued above. But let us have no illusions that the scuttling of the manned space program is actually an intelligent plan to improve it. More than a few scientists, who would have derided Bush as an anti-intellectual giving handouts to companies had he done this, are falling over themselves to buy into Obama’s promises of next-generation lift technology to Mars, despite losing our capability of this-generation lift technology to the Moon. Yet I have been exposed to the academic community long enough to know that liberal sympathies trump logic, notwithstanding their pretensions of scientific objectivity.