There may have been Life on Mars, say two geo-scientists who have been studying hot springs in Chile and found silica deposits with structures influenced by living organisms, which are surprisingly similar to a location visited by NASA’s Spirit rover in 2007 when one of its wheels got stuck and turned over the Martian soil like a plow.
Life on Mars, as far as Hollywood and science fiction comics in the 20th century were concerned, was all about little green men. Perhaps by looking for more subtle ‘biosignatures’, our chances of finding compelling evidence of present or past life on Mars will improve considerably, say Jack Farmer and Steve Ruff, from Arizona State University’s School of Earth and Space Exploration.
A biosignature is any substance – such as a molecule, element, isotope or phenomenon – that provides compelling or scientific evidence of past or current life.
This image of a cluster of fingerlike silica nodules was captured by NASA’s Spirit rover on Mars, near Home Plate in the Columbia Hills in 2007. The nodules look virtually identical to the silica nodules at El Tato hot springs in Chile, where biological activity contributed to their formation. (Image: sese.asu.edu. Credit: NASA/JPL-Caltech)
In their report, published in the prestigious journal Nature Communications (citation below), their discovery of possible ancient life on Mars involves fingerlike structures that form in the hot spring deposits by processes that combine non-biological and biological activity.
Chile is home to the world’s driest desert – the Atacama Desert. At the edge of the Atacama is a place called El Tatio, one of the best ‘Mars analog’ sites on Earth with some fascinating hot springs.
They found silica deposits at El Tatio with structures influenced by living organisms that appear virtually identical to those found in 2007 by NASA’s Spirit rover in Gusev Crater on the Red Planet (Mars).
Did Spirit find evidence of life on Mars?
The authors asked themselves the first logical question after noticing the similarity – had Spirit discovered evidence of life on Mars? Were those structures also influenced by life?
These fingerlike nodules found at the El Tatio hot springs in Chile are virtually identical to those photographed on Mars by NASA’s Spirit rover. The ones in Chile grew with the activity of microorganisms – life forms. Did the ones on Mars too? (Image: sese.asu.edu. Credit: Steve Ruff)
Lead author, Prof. Ruff, a planetary geologist with a focus on the mineralogy of Mars, said:
“Mars exploration has reached a stage where we can start looking for biosignatures.”
Our most common examples of evidence of past life on Earth are fossils. However, biosignatures can come in many shapes and sizes, some right-in-your-face obvious, and others more subtle, such as organic molecules trapped in a rock.
Some physical structures may be forms of biosignatures, including stromatolites – compacted mats of microorganisms – found in various environments on our planet.
None of the devices that humans have sent to Mars have detected any fossils. So, researchers assume that any biosignature – evidence of life on Mars – is going to be super tiny. It will be microscopic and hard to identify, let alone even find. Mars’ surface area is about the same as all the land areas on Earth.
Ancient life on Mars in Columbia Hills?
Eight years ago, NASA’s rover Spirit, also known as MER-2 (Mars Exploration Rover – 2), a robotic exploratory vehicle that was active from 2004 to 2010, was exploring an eroded deposit of volcanic ash that scientists had dubbed Home Plate, in the Columbia Hills of Gusev Crater.
Its right front wheel got stuck, and as the rover dragged the faulty wheel it dug up the soil like a plow. It uncovered a rich deposit of pure silica – also known as silicon dioxide or SiO2 – surrounded by silica-rich outcrops.
Looking for life on Mars — in Chile https://t.co/PkB3a7Zd0F
— SESE (@SeseASU) November 17, 2016
Silica, a mineral, is commonly found in geysers and hot springs like the famous ones in Yellowstone National Park.
Prof. Ruff was one of the researchers who identified the silicon dioxide and, along with Jack Farmer, Professor of Geobiology at Arizona’s School of Earth and Space Exploration, published observations supporting a hot spring origin. However, the uncommon and fingerlike structures of the silica outcrop next to Home Plate were not well understood.
Looking for comparisons
Prof. Ruff learned about the hot springs at El Tatio from a scientific publication a few years later. These hot springs, at 14,000 feet, are among the highest known active thermal springs on our planet.
At night, temperatures in the area regularly drop below freezing, even in the summer months. During the day, lots of ultraviolet sunlight comes through the thin, dry air, making El Tatio one of the best terrestrial analogs for ancient Martian hot springs.
Prof. Ruff said:
“We went to El Tatio looking for comparisons with the features found by Spirit at Home Plate. Our results show that the conditions at El Tatio produce silica deposits with characteristics that are among the most Mars-like of any silica deposits on Earth.”
These features compare favorably with the Martian Home Plate silica outcrops. Prof. Ruff explained:
“The fact that microbes play a role in producing the distinctive silica structures at El Tatio raises the possibility that the Martian silica structures formed in a comparable manner – in other words with the help of organisms that were alive at the time.”
What about the next rover?
A new NASA rover – yet unnamed – will be sent to Mars in 2020. It will be similar to the Curiosity rover in power and size. Curiosity is exploring Gale Crater at the moment.
The new rover’s instruments will be more advanced than those of its earlier cousins. It will be able to gather and cache samples for later retrieval.
For our best chances of finding evidence of life on Mars, where should the new rover go? NASA has held a number of workshops in which scientists present their case for specific landing sites.
When each workshop ends, candidate sites are ranked in order of fitness regarding certain qualities, including the potential for finding evidence of current or past life on Mars, the quality of returned samples, and geological setting.
In the league table of best sites, the Columbia Hills/Home Plate site in Gusev Crater is in second place, out of a total of eight candidates. Number one is an ancient lakebed in Jezero Crater on the northwest edge of an old impact basin called Isidis Planitia.
The next site selection workshop will be held in February 2017. NASA plans to reduce it to a shortlist of four candidates – the ‘Final Four’.
Going to Gusev’s Columbia Hills and Home Plate sounds exciting, given what we now know. However, it would mean not exploring a completely new area of the Red Planet – something many scientists would love to do.
Professors Farmer and Ruff obviously want the new rover to land near the Columbia Hills/Home Plate site. They say they are hopeful – that its chances are fairly good.
Prof. Ruff said:
“This is a known hydrothermal deposit. We know exactly where to land and where to go collect samples. And the silica structures found by Spirit meet the definition of a potential biosignature.”
Citation: “Silica deposits on Mars with features resembling hot spring biosignatures at El Tatio in Chile,” Steven W. Ruff & Jack D. Farmer. Nature Communications 7. November 17, 2016. DOI: 10.1038/ncomms13554.
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