...from recent issues of "Science":
(1) Apr. 26 (pg. 647-8): "Salty water is a comforting home for life today, but it probably was too harsh for the first cells. That's the surprising conclusion of new lab studies, which found that primitive membranes and chains of basic genetic material assemble far more easily in fresh water. The research suggests that life arose in ponds on the earliest continents, rather than in tide pools or the deep sea, as many researchers have assumed." This is not good news for the prospects of Europan life, given the likelihood that its ocean is far brinier than Earth's ocean has ever been. (That's especially so when combined with conclusion in Europa Focus Group that high acidity is also fatally destructive to the initial evolution of life out of prebiotic molecules.) (2) May 10 (pg. 1056-8): Geologists have "said that 'probably the top few kilometers of the entire basaltic ocean crust is alive with microbes.'... The recognition of pervasive, all-enduring life has sparked visions of alien life just waiting to be found beneath the inhospitable surface of Mars. Researchers exploring the deep subsurface here on Earth -- continental crust, marine sediments, and ocean crust -- are not so optimistic, however. They are finding deep life, but it mostly seems to be living indirectly off the eenrgy of sunlight rather than using local, less tempting sources of energy, such as the rock itself. Even when feeding off organic matter that trickles down from plant life at the surface, deep microbes are usually starved into apparent dormancy; when cut off from photosynthetic fuel supplies, they simply disappear... What deep life they are finding [even when temperatures allow it] is living 'very, very slowly'. " (3) May 24 (pg. 1384-5): "What lingering traces -- a smudged imprint in rock, an oddly composed bit of organic matter, or distinctively imbalanced isotopes -- might show that life existed eons before? For almost two centuries, paleontologists wrestling with that problem have pushed the earliest known life back in time... [using] wormy squiggles in the mud and vanishingly small fossils. And in the past few years, egged on by a claim for traces of life in a 4.5-billion-year-old rock from Mars, researchers have explored new kinds of biomarkers -- molecules and isotopes -- in very ancient rocks. But interpreting both new and old kinds of markers has proven more complicated than many had hoped, and the results have sparked several heated debates. "In this issue of 'Science', for example, two geologists challenge a startling claim for the first signs of life: that the skewed isotopic composition of graphite in rock from an island off Greenland shows that life existed 3.85 billion years or more ago, when huge, globe-sterilzing impacts were still battering the planet. The debate highlights the growing realization that as analyses become ever more high-tech, relying on tinier samples and subtler traces, it becomes more important to understand the [geological] environment in which a presumed biomarker formed... 'We had a very optimistic view of how easy it was going to be to recognize the signs of life,' says meteoriticist Harry McSween... 'We have a lot of work to do.'... "Such setbacks are reminding researchers that life usually doesn't leave a unique trace; in many cases, what organisms do, inorganic chemistry can too. 'It's not enough to say, 'Here's a biomarker that organisms produce", ' says meteoriticist Ralph Harvey.. 'You have to say, "Here's why it can't be produced other ways." That's a much bigger problem.'... 'If the specialists cannot agree on the quality of evidence from terrestrial rocks,' asks Queensland's Balz Kamber, 'what hope is there to agree on evidence from tiny meteoritic fragments or returned samples?'.. [However], with the impetus from ALH84001 and [an increased] commitment to the interdisciplinary investigation of geological context, biosignatures could work, researchers say." == You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
