Why is NASA so interested in Mars? Consider the Bonneville Salt Flats
NASA’s Curiosity Rover survived its 7 Minutes of Terror and touched down successfully on the Red Planet’s surface late last night. Watching NASA TV’s live coverage of the event was exciting for two reasons. First, it was a raw peek into the minds of the scientists and engineers who have eaten, slept, and breathed this mission for years. Relief, exhaustion, elation– all on uninhibited display. I’m always amazed by the ordinary-looking people who figure out how to shoot something into space and make it land on an alien world in one piece. That first image of the Martian surface was priceless; the awkward high fives in JPL’s Mission Control last night were even more so.
Second, the event was punctuated by a renewed interest in Mars and the U.S. space program in general. Most NASA followers would acknowledge that public interest in launches and missions has waned considerably over the years. What’s more, to much of the space community, the demise of the Shuttle Program last year signaled the end of America’s grand space exploits. NASA-philes and the public alike were in desperate need of a new space success– some mind-blowing feat to rally around. Curiosity didn’t disappoint.
But why Mars?
I wrote the following story late last year for the 2012 edition of Tooele County Magazine while Curiosity was yet en route to Mars. It’s focus is the Mars Opportunity Rover and the Martian connection to our own Bonneville Salt Flats. It answers the “Why Mars” question and may motivate you to begin following both Opportunity and Curiosity on Twitter. Enjoy.
It’s February 10, 2004—at least as Earth reckons it. The Gregorian calendar is irrelevant on the Red Planet, and is of little significance to the robotic dune-buggy that creeps along its surface. To NASA’s Mars Opportunity Rover, it is Sol 17—the seventeenth Martian day since it touched down in a small impact crater on the planet’s Meridiani Planum and began sending digital postcards 123 million miles back to Earth.
With its elevated camera rig mounted atop a six-wheeled chassis, Opportunity Rover looks like a mash-up of Disney-Pixar’s WALL-E and the Johnny 5 robot from the movie Short Circuit. It’s almost anthropomorphic guise is appropriate for its purpose: to act as proxy for humanity on Mars. Indeed, each of its movements is choreographed and remotely initiated by a handful of scientists and engineers at NASA’s Jet Propulsion Laboratory in Pasadena, CA. Of particular interest to the Mars Exploration Rover (MER) team is a rock outcropping on the crater’s rim that Opportunity photographed shortly after landing. Stone Mountain, as the MER team quickly dubbed it, was a mere 32 feet away from Opportunity’s position. It would be the rover’s first destination on Mars.
After two weeks of cautious driving, the rover has finally arrived at Stone Mountain. It extends its hinged arm toward the formation to take a spectral reading, then beams the results to its eager controllers on Earth. The analysis is staggering. The rock is composed of nearly 40 percent sulfate salt, including jarosite, which on Earth only forms in the presence of liquid water. The discovery is a solid entry in the growing body of evidence that Mars was once capable of supporting life.
Fast forward to 2011. Opportunity is still alive and rolling more than seven years past its original 90-day life expectancy, and two years after its twin, Spirit Rover, became stuck in a cache of loose jarosite and eventually died. Having arrived at Endeavor Crater in August, Opportunity continues to gather evidence of a wetter Martian past. Meantime, its space-bound counterpart, the Mars Reconnaissance Orbiter (MRO), snaps photos from above. In fact, MRO Images released by NASA in August 2011 show what appear to be active seasonal brine flows.
Yes, active. Let that sink in for a moment.
In the context of human history, the reality of exploring another world—even via remote control—is nothing short of miraculous. The cost and effort involved in these missions are a testament to mankind’s irrepressible urge to, as one fictional explorer put it, “seek out new life.”
And yet, as successful as NASA’s Mars Exploration Program has been thus far, exploration of the planet with current technology is stifled by one maddening limitation: distance. The average distance between Earth and Mars is 49 million miles (depending on their positions in their respective elliptical orbits around the sun). For comparison, the average distance between Earth and the Moon is approximately 240,000 miles. The vast gulf between Earth and Mars makes manned missions yet infeasible and forces our reliance on these mind-bogglingly advanced, yet very delicate robots. Since landing in 2004, Opportunity has traveled just over 20 miles at an average speed of 0.00037 mph. Even the simplest rover behavior involves numerous lines of computer code transmitted once daily. Furthermore, Opportunity is incapable of sending physical samples back to Earth.
Simply put, actual hands-on exploration of Mars could be decades away. But since when have time and distance ever stopped us?
The search for life—or at least for conditions that might sustain it—led us to Mars, not because of its pop culture notoriety, but because science tells us it’s a likely candidate. The two planets are similar in land surface area, atmospheric chemistry, and rotational tilt. Like Earth, Mars’ topography shows evidence of historic climate variation. Mars is also a convenient candidate for study since many extreme Earth environments are geologically analogous to it.
Opportunity Rover’s salt discoveries, and the possibility of active brine flow on Mars, raise some bold, yet valid questions. Might the similarities between the sibling planets be biological as well? If some kind of crazy extreme life form was discovered on Earth, might it also have existed under similar circumstances on Mars? Might it still exist there?
Two months after NASA released those ground-breaking MRO images of possible active brine flows, I’m standing at the edge of the Bonneville Salt Flats, just northeast of Wendover. The flats, a 50-square mile salt playa, are a relic of ancient Lake Bonneville, which covered most of present-day Utah for tens of thousands of years. According to Dr. Marjorie Chan, professor of Geology and Geophysics at the University of Utah, understanding Lake Bonneville is key to understanding Martian water bodies. Its imprint on Utah’s geography includes a wealth of deltas, playas and terraced benches that enshrine a detailed geologic history. The Bonneville Basin is something of a Rosetta stone for studying groundwater flow on Mars.
In that context, the Bonneville Salt Flats are an analog within an analog. Not only do the flats look like alien terrain, they bear a striking geological resemblance to Meridiani Planum, Opportunity’s Martian home turf. But I’m not here for the rocks. I’m here because of biology professors Bonnie Baxter, Ph.D. and Betsy Kleba, Ph.D. of Westminster College in Salt Lake City. They intend to prove that despite popular belief, this mysterious world of salt and interminable space, is far from dead.
It’s late October and the flats are flooded with a shallow layer of brine, onto which the nearby Silver Island Mountains cast an eerily perfect reflection. This seasonal phenomenon results from year-round groundwater flow and is part of the playa’s natural rejuvenation cycle. Come spring the brine will begin to evaporate, leaving behind a fresh layer of bleach-white salt.
Crouching at the end of a spit, Dr. Baxter pulls a refractometer—an instrument used to measure the salinity of water—from her bag and dips it into the brine. “Oh my heavens,” she exclaims as she looks through its lens toward the sun, “It’s right at thirty percent!”
That’s slightly less salty than the Dead Sea, slightly saltier than the Great Salt Lake’s north arm, and nearly nine times saltier than seawater. The Dead Sea aside, one seems hard pressed to find an earthly environment more inhospitable to life. And yet, this hypersaline environment is teeming with countless primitive microorganisms appropriately called “extremophiles.”
Baxter and her colleagues have spent the last 15 years harvesting and documenting novel halophilic (Greek for “salt-loving”) microbes, mostly from the Great Salt Lake’s saltier north arm. The majority of them have been archaea, a type of single-celled microbe considered by scientists to be analogous to the oldest forms of terrestrial life. Today will mark Baxter’s first major sampling at the salt flats. She and Kleba comment excitedly on the flats’ otherworldly aesthetic as they unpack their sample kits.
Baxter’s passion for the Great Salt Lake and its environs became immediately apparent during a pre-trip interview.
“Great Salt Lake is such an icon,” she said, lauding its vital role as an extreme ecosystem. “But historically, everybody has been very irritated by it. I like to imagine that native peoples had a reverence for the flats and the lake.”
At that point, I thought it wise to refrain from sharing my childhood dream of walling off and diluting Stansbury Bay, then installing a wave generator, importing dolphins, and planting winter-tolerant palm trees—you know, so it could be more like the realocean. Instead, I pointed out that however modern Utahns might feel about the lake, the Mormon Pioneers were enamored with it and spent as much time on its shores as they could. My own fascination with the lake today lies in its geology and dissonant visual appeal. I hadn’t thought much about the biology—at least not on the microscopic level. And I wasn’t alone.
“It’s both a tragedy and an opportunity,” added Baxter. “If I’m the expert on [Great Salt Lake microbiology], it’s mostly because nobody else was doing this.”
A native of rural North Carolina, Baxter credits two particularly excellent middle school teachers for helping her discover a passion for science.
“A lot of people write off rural teachers, but they’re critical pieces to the social puzzle,” she said.
After earning her Ph.D. in Genetics at the University of North Carolina, Chapel Hill, Baxter moved west for post-doctoral research and fell in love with the Great Salt Lake. Her interest in microbiology of the salt flats was sparked by Physical Scientist Bill White of the U.S. Bureau of Land Management. He discovered bright green algae growing inches underneath the flats’ surface.
“I knew Bill White as a salt expert and he knew me as a salt-biology expert,” said Baxter. “He wanted to share what they were consistently finding, which was that algae was growing in the layer between the Gypsum and the Halite!”
As a professor at Westminster College, Baxter helped establish the Great Salt Lake Institute in 2008. She currently serves as its director. GSLI promotes education, research, and cooperation between universities and other organizations on all aspects of the lake.
Betsy Kleba earned her Ph.D. in Infectious Diseases and Immunity from the University of California, Berkeley. She joined Westminster as an associate professor in 2010 after post-doctorate work in Montana, where she also taught at the University of Montana and numerous middle schools. Last summer she and two students began work to characterize some of the novel microbes that Baxter had collected from the Great Salt Lake.
Kleba has a knack for explaining complex cellular processes in such a way that even non-scientifically oriented minds like mine can follow. She has me grasping concepts like microenvironment preference and cell growth within minutes of our arrival at the salt flats.
After determining the water’s salt saturation, the first thing both biologists note is the lack of a pink hue in the brine. Most halophilic microbes produce a pigment that protects them from ultraviolet rays, and in turn, gives the water a pinkish hue.
“The pink water near the salt refineries and up in the north arm—those are our halophiles,” Baxter explains.
“Everywhere in the world where there is a high concentration of salt, the water turns pink. So why isn’t this pink?”
The existence of microbes in this environment never comes into question. Of that, Baxter and Kleba have no doubt. They wonder if conditions here may not require the pigment—another good reason to harvest samples. The study of halophiles in and around the Great Salt Lake is still in its infant stages. Many of the microbes that thrive here have never been identified by science and are still unknown.
Much of the preliminary analysis is visual, but these halophiles are unique even at that level. Microbes are typically distinguished by rod, sphere and spiral shapes. “But we’ve seen all kinds of different shapes,” Baxter says. “Particularly squares. We also see these little pyramids and crescents.”
She adds, “The squares have been very difficult to cultivate.”
The work of Baxter and others has revealed several basic characteristics of halophiles. They flourish in hypersaline environments by maintaining a cocktail of salts, lipids and sugars inside their cellular membranes to balance the salt outside. It’s a delicate balance. Too much salinity inside and the cell withers; too much outside and it bursts.
The key to maintaining this balance is a protein called bacteriorhodopsin, which harnesses energy from light to pump salt ions across the cell’s membrane. “So these microbes literally swim toward the light,” Kleba explains.
Aside from their salt tolerance and natural UV protection, halophiles are able to survive desiccation (extreme dryness). They’re often found locked in a mineral matrix—their DNA nearly perfectly preserved. Baxter and colleagues recently found 250 million-year-old microbial DNA in a New Mexico salt mine. Just how long these organisms can survive in a desiccated state is unknown, but Baxter has successfully resuscitated recently desiccated microbes.
“These microbes can live virtually without water,” she says. “There’s a salt flat on Mars and we think water used to be there. If the water on Mars is gone but the salt is still there, could the microbes be dried up and hanging out in the salt crystals just like they do on earth? We have to understand these unusual life forms on our planet, so that when we do get samples from Mars, we’ll know what to expect.”
Baxter’s interest in hypersaline ecosystems extends to Earth applications as well. The lipids involved in salt balance, for instance, may lead to advances in bio-fuel development. Halophiles’ UV defense could be replicated for use in sunscreens. The environmental and medicinal implications might be boundless.
Baxter and Kleba spend the next hour chipping salt samples from the spit and filling several bottles with brine. They’ll take them back to their laboratory at Westminster, where they’ll “plate” and incubate them. It will be several weeks before the microbes multiply enough to be analyzed. Baxter thinks they’ll turn out to be archaea, and she expects that at some point they’ll turn pink.
Two weeks later, I visit Kleba at the lab at Westminster. The salt flats samples are still premature, but Kleba pulls several already developed cultures from an incubator. Their colors range from pink to orange. Individual cellular communities—clumps of billions of multiplied cells—appear as small dots to the naked eye.
“What excites me most about starting this new line of research is that it has the potential to bring all of my scientific interests together,” says Kleba. “If we can identify and characterize organisms with unique metabolic capacities, we can then begin to understand the role these microbes play in the ecology of Great Salt Lake—and potentially harness their metabolic capacity in a way that can be useful to human-kind as well.”
I follow up with Baxter and Kleba in late December. Just as they suspected, the salt flats samples have grown and begun to yield white, pink, and red colonies. The variation suggests the presence of multiple types of organism, and the biologists have started separate cultures for each colony. Identifying them will require several more weeks of growth and analysis.
In the meantime, the Mars Curiosity Rover, launched on Nov. 26, 2011, is making its way to the Red Planet to continue the mission of its forerunners. The nearly one-ton buggy is expected to land in early August 2012 at Mars’ Gale Crater.