Key assumptions about habitability on Mars have fallen, but astrobiologists try to keep hope alive.
By gully, no water there. When first seen, gullies on the walls of certain Martian craters were announced as strong evidence for water. Even though water cannot exist on Mars’ surface now, scientists felt subsurface water could be temporarily liberated to flow down the crater walls and carve the gullies. Now, Science Daily says, “Mars gullies likely not formed by liquid water.” Improved imaging data from multiple wavelengths has undermined the watery explanation. “The findings showed no mineralogical evidence for abundant liquid water or its by-products, thus pointing to mechanisms — such as the freeze and thaw of carbon dioxide frost — other than the flow of water as being the major driver of recent gully evolution.” Since life needs water, this undermines hopes for finding life at these sites. While the findings do not rule out water, scientists think it would consist of “small amounts of brine” incapable of forming the gullies.
Forced sterilization. Astrobiologists don’t expect life to be found on the surface of Mars due to the planet’s high radiation exposure (9/05/14). Instead, they hope to find it deep underground. Now, Space.com asks, “Did Meteorite Impacts Sterilize Subsurface Mars Life?” Discovery News writer Ian O’Neill has bad news:
The sites of meteorite impacts on Mars are often considered to be good places to look for life. After all, it’s most likely that if any trace of life (past or present) ever took hold on the Red Planet, it would most likely be preserved under the bedrock of Mars’ harsh surface. Should there be a recent impact, could we search the debris to seek-out this recently excavated pristine rock for life?
Alas, in new research, this kind of impact crater search could be a fool’s errand; the energy of the impact likely sterilized any material we’d consider organic and related to life.
Notice he says it would not have just killed life; it would have destroyed the organic material “related” to life. He ends without providing any empirical evidence for keeping hope alive. He just says, “we can’t assume that every crater will be a Mars biology goldmine.”
Astrobiology propaganda continues. Live Science takes a look at 20 years of research into the famous Allen Hills meteorite ALH 84001 that caused a big media stir in 1996. At a NASA press conference, David McKay and colleagues presented tantalizing hints of fossilized organisms inside the rock. The photo in Live Science’s story showing a worm-like structure was replicated around the world. Shortly afterward, a new science was born: “astrobiology.” NASA formed its Astrobiology Institute that continues to this day funding projects to look for life beyond the earth. “Without this paper, the field of astrobiology may never have come to exist,” comments Carnegie Institute astrobiologist Andrew Steele. This could be interpreted that without the paper, he wouldn’t have a job.
In retrospect, though, Timothy Swindle of the University of Arizona finds that skepticism has grown in the interim. In 1996, he had interviewed 100 colleagues and determined that scientists felt it was a completely open question whether life could exist on Mars. This was 20 years after the 1976 Viking landers, having failed to detect organic molecules in the Martian soil, dashed the optimistic hopes of that era. Viking was 12 years after the first Mars visit by Mariner 4 sent back images of a Mars not lush with canals, forests, and intelligent civilizations (as popularized by Percival Lowell) but looking like a crater-pockmarked desert.
Swindle and many others are skeptical that ALH 84001 provided evidence for life, but the original authors maintain their story. Even the skeptics acknowledge that some good came from the announcement. It generated a lot of research to try to prove or disprove the claim, and it gave a shot in the arm to the Mars program that produced the orbiters and rovers that have fascinated the public. Still, no evidence of life has ever been found. The news about dry gullies and sterile craters is likely to reinforce a trend in our perception of Mars: it has a lot of interesting geology, but no life.
What kind of justification is that? Suppose scientists announced evidence for ghosts on Mars. A swarm of studies and publications follows to prove or disprove the claim. NASA launches a Ghostology Institute, using public funds, to continue the search. Ghostbuster Rovers land on the red planet, looking under every rock for evidence of the elusive beings. Twenty years later, the ghosts remain undiscovered, but scientists justify the original claim that it did a lot of good because of all the research it generated. “Without it,” a beneficiary exclaims, “the field of ghostology would never have come to exist.” Would that be a Swindle, Timothy?
Space exploration needs astrobiology like Roald Amundsen needed Darwin’s storybook in his pack to reach the South Pole. We explore because things are there. It’s in our nature to discover. Instead of bamboozling the public with NASA propaganda endlessly promising to find life that never shows up, we have a better idea. Promote space exploration on these grounds: We will never fully understand how exceptional the Earth is for life without comparing it in detail to other bodies in the solar system and around other stars. That’s truthful; that’s empirical; that is sufficient.