For those who were expecting confirmation of the discovery of little green men or Decepticons or even traces of microbial life, you will probably be disappointed. After rampant (and viral) internet speculation, NASA is expected to make an announcement at noon EST today about the progress and scientific achievements of its Curiosity rover during this week’s Fall Meeting of the American Geophysical Union (AGU). The meeting, which begins today in San Francisco and runs through to Friday, will include the long-awaited Curiosity news conference which NASA describes as “an update about first use of the rover’s full array of analytical instruments to investigate a drift of sandy soil.” Officials at the Jet Propulsion Laboratory in Pasadena, Calif., have stressed that rumours about a dramatic new discovery “at this early stage are incorrect.”
The speculation arose in mid-November, when Curiosity’s chief scientist, John Grotzinger, was quoted as saying that the Sample Analysis at Mars (SAM) instrument had gathered data “for the history books.” Since SAM is designed to identify organic compounds in the Martian soil, it was assumed by many that the $2.5 billion, six-wheeled rover—which landed beside the 18,000-foot peak of Aeolis Mons (“Mount Sharp”) in the yawning bowl of 96-mile-wide Gale Crater in early August 2012—had uncovered traces of microbial life. That mistaken assumption was corrected by NASA officials last week: “At this point in the mission,” it was clarified on 29 November, “the instruments on the rover have not detected any definitive evidence of Martian organics.”
Yet Curiosity has made enormous inroads in our understanding of the nature of the Red Planet since touching down at a place now known as “Bradbury Landing”—in honour of the late science fiction writer Ray Bradbury—just one hundred and twenty days ago. It is barely a sixth of the way through its projected two-year primary mission to investigate whether the Gale Crater region was ever suitable to sustain microbial life. In fact, Mars’ close proximity to both our own planet and to the Sun has fuelled serious scientific discussion for more than a century that the blood-hued world may have produced organics at some stage. The possibility has inspired movies and books and posters and games and even today the lure of the planet remains inescapable.
As early as the late 18th century, Mars’ polar ice caps were observed growing and shrinking with the onset of winter and summer in each hemisphere by William Herschel, and within a handful of decades the first suggestions were made that it may harbour seas, land, and possibly life. When Percival Lowell expressed his conviction that he had seen evidence of ancient canals on Mars, his adherents were captivated. Early spectroscopic observations of the Martian atmosphere seemed to reduce the likelihood of life, but that did nothing to dispel the excitement. H.G. Wells published his War of the Worlds in 1897, and Orson Welles’ famous—and famously terrifying—radio version in 1938 convinced many that not only was Mars inhabited, but it was inhabited by a hostile species.
Indeed, the planet has been hostile to many of our robotic emissaries, with fewer than half of all spacecraft successfully entering orbit or touching down safely on its red surface. When NASA’s Mariner 4 flew past Mars in July 1965, it revealed its truly arid nature, devoid of rivers or canals and with very little evidence of plate tectonics or weathering for at least the last several billion years. A decade later, the Viking landers arrived and found no conclusive evidence for the existence of organic material in the soil. Much later, in May-November 2008, the Phoenix lander revealed pH and salinity levels in the Martian north were relatively benign from a biological perspective, but that other aspects of the local geology made it somewhat less friendly to microbial life. Curiosity’s landing in August 2012 is expected to kick off a mission of at least two years to further investigate the possibility that evidence for the building blocks of life is entrenched within the Martian soil, awaiting discovery.
One such building block has, and continues to be, the presence of water-ice in significant quantities. Low atmospheric pressures and temperatures on the surface render it unlikely for anything capable of sustaining Earth-like life, although the discovery by Mars Express of water-ice reserves in the south pole in January 2004 and confirmation from the Opportunity rover the following March that Mars was, historically, a “wet” planet, lend credence to the possibility that conditions were more suitable in the distant past. More recently, data from the Mars Global Surveyor suggested that water might occasionally flow on the surface, although this conclusion has been met with scepticism in some quarters of the scientific community.
As for the future exploration of the Red Planet, funding presently hangs in the balance. Earlier this year, NASA budget cuts forced the space agency to cancel its involvement in the ExoMars mission with the European Space Agency, although several websites have noted a possibility that the forthcoming Space Launch System may be employed on a Mars Sample Return mission in the mid-2020s. For now, however, we have the six wheels of Curiosity firmly planted in Gale Crater and after only four months on the surface, its Twitter feed already boasts 1.2 million followers and every report on its progress draws excited speculation. Even if today’s news conference reveals nothing more than a ho-hum update on its scientific progress, the prognosis for the remainder of its mission—and the chance of spectacular, ground-breaking discoveries—remains high.