Nearing the limits of life on Earth

Nearing the limits of life on Earth
The average daily air temperature in the Antarctic summer of 2013, when Goordial collected the permafrost samples which she tested both on the spot and later in the lab, was -14 °C and it never rose above 0 °C, making the permafrost difficult to drill. Credit: Jackie Goordial

It took Jackie Goordial over 1000 Petri dishes before she was ready to accept what she was seeing. Or not seeing. Goordial, a post-doctoral fellow in the Department of Natural Resource Sciences at McGill University has spent the past four years looking for signs of active microbial life in permafrost soil taken from one of the coldest, oldest and driest places on Earth: in University Valley, located in the high elevation McMurdo Dry Valleys of Antarctica, where extremely cold and dry conditions have persisted for over 150,000 years. The reason that scientists are looking for life in this area is that it is thought to be the place on Earth that most closely resembles the permafrost found in the northern polar region of Mars at the Phoenix landing site.

"I've been trying to cheer her up by telling her that not finding life is important too," says Lyle Whyte, Goordial's supervisor. "Going into the study, we were sure that we would detect a functioning and viable microbial ecosystem in the of University Valley as we and others have done in Arctic and Antarctic permafrost, including in other sites at lower elevations in Antarctica. It is hard for both of us to believe that we may have reached a cold and arid threshold where even microbial life cannot actively exist."

Drilling for microbes in Antarctica

What brought the researchers to University Valley was a NASA ASTEP (astrobiology science and technology for exploring planets) project to test the IceBite auger, a permafrost drill designed to drill into Martian permafrost. The average daily air temperature in the Antarctic summer of 2013, when Goordial collected the permafrost samples which she tested both on the spot and later in the lab, was ? 14 °C and it never rose above 0 °C, making the permafrost difficult to drill.

Nearing the limits of life on Earth
Denis Lacelle of University of Ottawa (left) and Alfonso Davila of NASA/SETI (right) operate a motorized ice drill to obtain cores in ice-cemented ground in University Valley. Credit: NASA/Chris McKay

The McGill team analyzed samples from two permafrost boreholes which reached a depth of just 42 cm and 55 cms below the surface. This may not sound like a lot, but drilling into permafrost to get soil samples for testing is very difficult.

"Anytime you drill into frozen ground and it has some ice in it the drilling process creates friction which melts the ice. The hole will refreeze within seconds if the drilling is interrupted, freezing the drill bit into the hole" says Whyte." I remember drilling in the Arctic and losing a drill bit in one of the holes we had made, just because it froze into the ice before we could get it out."

"Previous studies in the lower dry valleys of Antarctica and in subglacial lakes were giving us the impression that microbial life was rich in the cold regions. But this is finally Mars!" says Chris McKay of NASA's Ames Research Centre. "University Valley has the coldest driest soil we can find on Earth. And life is really having a hard time of it there. This is certainly the training ground for the search for evidence of life on Mars and an extremely important result for NASA's astrobiology effort."

Nearing the limits of life on Earth
In University Valley, there is a layer of dry permafrost soil overlaying ice-rich permanently frozen ground. The ice in the permafrost is formed not by liquid water, but by frozen water vapor; the absence of liquid water, makes the soil less likely to be able to sustain life. Credit: Jackie Goordial

All the tests came out negative

The research team carried out a variety of tests, both in the field (where they failed to find evidence of carbon dioxide or methane - a gas used by all living things - in the soil) and then back in the lab at McGill in Montreal. They sent soil samples for DNA testing, looking for matches with particular genes known to be found in microbes and fungi; they tried to stimulate microbial growth on a wide variety of substances and then count the cells produced; and they used highly sensitive radiorespiration activity assays, which involve feeding the soil microorganisms a food source which has been labelled with radioactive carbon, which can then be used to detect if the microorganisms are active.

The tests failed to show any signs of active life.

"We couldn't detect any microbial activity within these samples," says Whyte. "Any, very limited traces we were able to find of microbial life in these samples are most likely the remnants of microbes that are dormant or are slowly dying off. Given the continuous dryness and subfreezing temperatures, and the lack of available water, even in summer, it is unlikely that any microbial communities can grow in these soils."

Goordial adds, "We don't know if there is activity beyond our limits of detection. All we can say for sure is that after using all the current methods of testing available to us, the samples are unlike any other permafrost we have encountered to date on Earth"

Implications for the search for life on Mars

"If conditions are too cold and dry to support active on an analogous climate on Earth, then the colder dryer conditions in the near surface on Mars are unlikely to contain life." Says Whyte. "Additionally, if we cannot detect activity on Earth, in an environment which is teeming with microorganisms, it will be extremely unlikely and difficult to detect such activity on Mars."

On a positive note however, the researchers add that this suggests that any microorganisms that may be transported to Mars from Earth by mistake are unlikely to be able to survive on the Martian surface, something that is of current concern for planetary protection.

Explore further

Antarctic offers insights into life on Mars

More information: To read "Nearing the cold-arid limits of microbial life in permafrost of an upper dry valley, Antarctica" by Jacqueline Goordial et al in The ISME Journal: DOI: 10.1038/ismej.2015.239 ,
Journal information: ISME Journal

Provided by McGill University
Citation: Nearing the limits of life on Earth (2016, January 19) retrieved 23 October 2019 from
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Jan 19, 2016
I am greatly saddened. I suppose I had unrealistic hopes for the adaptability of life.

Given that briny water appears to be seeping from crater walls on some parts of Mars, is University Valley actually more arid than Mars?

Hopefully, someone's running experiments to see if microbes can survive Martian sub-surface conditions in the presence of perchlorate brine.

(Crossing fingers)

Jan 19, 2016
The link near the bottom of the article to leads to an error page. The actual paper can be retrieved from http://www.nature...39a.html . The paper mentions a soil solute ("salt") concentration of "<5 g l−1 ... primarily of a SO4–NO3 geochemical composition" and with a near-neutral pH. This makes it unlike Mars soils, which are very alkaline and dominated by perchlorate salts at .5-1% (5-10 g/l).

Jan 19, 2016
Nature amazes again! A similar situation is seen when drilling the subsurface of ocean bottoms, where prokaryote activity (density) diminishes faster than an exponential. When you go to ~ 1.5 km depth (IIRC), the conditions is much as here - buried cells are slowly dying. Of course, in both cases cracks and seeps would make for local habitability.

@Azrael, barakn: The recurrent slope lineae has a day temperature somewhere between -30 and 30 deg C (needs solar influx, so are heated at times), and on Earth the lower limit is something like -20 degC for procreating prokaryotes.

But the amount of salt could be a problem, the Gale crater morning "dew" brines went down to - 80 degC and were very salty - both conditions too severe for our own extremophiles.

Perchlorates are nutrients for some prokaryotes (in the Atacama desert, say), but I guess SO4/NO3 could be too, all are oxidants.

Jan 20, 2016
these fellows were unable to drill more than a few feet down. Let them drill a hundred feet, or 200 or more and look again.

Jan 20, 2016
If you can't find life in the harshest place on Earth how could you hope to find it on Mars? Mars is AT BEST as warm as this valley, and at worst 100 degrees colder, and it has been for hundreds of millions of years.

Jan 20, 2016
The cold and dry conditions are is just one facet of the hurdles that organic life would have to face to survive on Mars. There is also the lower solar radiation and much higher cosmic radiation as well as the lack of oxygen and free nitrates.

Jan 20, 2016
The reason(s) there is no life on Mars is due to the fact that without an active central core to produce magnetic waves as Earth has to protect living organism from harmful solar radiation! The very reason that if Mars had life, (probable) a dwindle effect of a dying central core would in essence kill off life as we know it in measured amounts of time. BTW it could happen to Earth if we lost OUR active central core!

Jan 21, 2016
Now it would be interesting to use ground samples from the same area to see if it could support microbial life introduced in a lab environment, and under what conditions it would survive. Maybe they could use microbial life from cooler regions in Canada, and see what happens. The research leads us to conclude that the surrounding environment can not support microbial life as there was none found, or it could not be measured based on the current methods. Similar to Mars, it would be interesting to find out when life could no longer exist, and under what conditions.

Jan 23, 2016
Transporting microbes to Mars.

We needed to start that back in the 60s. Maybe the Russians or Chinese can be talked into it? Mars will never be terraformed without importing Earth origin lichen, algae and bacteria. Oh! And we need to whack the planet with a couple of dozen (hundreds?) water rich asteroids and comets.

Jan 23, 2016
If there are animals and vegetation there must be bacteria.I think there are some life in the Antarctic

Jan 24, 2016
Heavy water (deuterium oxide is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium, rather than the common hydrogen-1 isotope that makes up most of the hydrogen in regular water. I wonder if any effort was made to detect heavy water,

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