September 24, 2012
Mars-Like Places On Earth Hint To Possible Life On Red Planet
Lee Rannals for redOrbit.com — Your Universe Online
Researchers set out to study some Mars-like places on Earth, giving new insights into rover data and conditions for life on the Red Planet.
The team presented the findings of their trip to Earth's Martian-like environments during a press conference at the European Planetary Science Congress.
Dr Felipe GomÃ©z, the project leader, and colleagues visited Chott El Jerid salt pan three times between 2010 and 2012, and Atacama desert in 2010.
They set up weather stations at a series of locations at each site, which measured surface and air temperatures, humidity, ultraviolet radiation levels, wind direction and velocity.
“We studied measurements in different locations over several daily cycles. As well as the large-scale changes to all the parameters through the day, we observed a small rise in the surface temperature after dusk," GomÃ©z said in a press release. "We found that this is caused by water condensing on the surface and hydrating salts, which releases heat in an exothermic reaction."
He said this is interesting because from the perspective of Curiosity's REMS instrument, it gives scientists a way to follow when liquid water might be present on the surface of Mars.
“The correlations we´ve found between these parameters and cloud cover means that we can use Mars orbiter measurements of cloud conditions to give us an indication of changes that are going on at the surface,” said GomÃ©z.
The researchers used probes to study the electrical properties of the soil, and were able to identify different materials underground and the water-content.
The team was able to build up a three-dimensional picture of the structure of the subsurface by setting up criss-crossing "transepts" of resistivity probes.
They also drilled samples to a depth of 12-feet in Chott El Jerid, and up to 20 feet in Atacama. The samples showed subsurface ecosystems of completely different kinds of bacteria from those found on the surface.
The populations of bacteria found at the surface decreased with depth, but there was an increase in archaea, and also single-celled halophilic organisms that are able to oxidize metabolites under aerobic and anaerobic conditions.
“In both Atacama and Chott El Jerid, we found ecosystems at a depth of a few meters that were completely isolated from the surface,” GomÃ©z said in the press release.
The surface of Chott El Jerid is pure sodium chloride with traces of other salts. The researchers found small accumulations of organic matter inside the salt crystals, and when they analyzed samples, they found these were populations of halophilic, salt-loving bacteria.
“This was a really exciting find," GomÃ©z said. "Gohese condensed accumulations of halophilic bacteria could have been dormant for possibly hundreds of years. Back in the laboratory, we were able to rehydrate the samples and restore the bacteria to life.”
The team also found photosynthetic bacteria growing between the layers of salt crusts at Rio Tinto. When they analyzed the bacteria back in the laboratory, they found that iron is protecting the bacteria from ultraviolet radiation.
“We took two samples of the bacteria, one with iron present and one without and exposed them to high levels of ultraviolet radiation," GomÃ©z said. "For the sample without iron, nearly all the bacteria were destroyed. For the sample with iron present the population survived. There was a small increase due to toxic super-oxides being created, but the protective effect of ferric compounds was significant.”
Their findings could help both current rovers on Mars, and future Martian explorers in the search for extraterrestrial life on the Red Planet.
“What the bacteria we found in Rio Tinto show is that the presence of ferric compounds can actually protect life. This could mean that life formed earlier on Earth than we thought. These effects are also relevant for the formation of life on the surface of Mars,” says GomÃ©z.
The scientists also found that salt provides stable conditions that can allow life to survive in very harsh conditions.
“Within salts, the temperature and humidity are protected from fluctuations and the doses of ultraviolet radiation are very low,” GomÃ©z said in the release. “In the laboratory, we placed populations of different bacteria between layers of salt a few millimeters thick and exposed them to Martian conditions. Nearly 100% of deinoccocus radiodurans, a hardy type of bacteria survived being irradiated. But fascinatingly, about 40% of acidithiobacillus ferrooxidans — a very fragile variety of bacteria also survived when protected by a salt crust.”