Field Geology on Mars Reveals Evidence of Megaflood

Guest “field geology rocks!” by David Middleton

Field geology at Mars’ equator points to ancient megaflood
By Blaine Friedlander | November 18, 2020

Floods of unimaginable magnitude once washed through Gale Crater on Mars’ equator around 4 billion years ago – a finding that hints at the possibility that life may have existed there, according to data collected by NASA’s Curiosity rover and analyzed in joint project by scientists from Jackson State University, Cornell, the Jet Propulsion Laboratory and the University of Hawaii.

The research, “Deposits from Giant Floods in Gale Crater and Their Implications for the Climate of Early Mars,” was published Nov. 5 in Nature Scientific Reports.


“We identified megafloods for the first time using detailed sedimentological data observed by the rover Curiosity,” said co-author Alberto G. Fairén, a visiting astrobiologist in the College of Arts and Sciences. “Deposits left behind by megafloods had not been previously identified with orbiter data.”


The most likely cause of the Mars flooding was the melting of ice from heat generated by a large impact, which released carbon dioxide and methane from the planet’s frozen reservoirs. The water vapor and release of gases combined to produce a short period of warm and wet conditions on the red planet.


The Curiosity rover science team has already established that Gale Crater once had persistent lakes and streams in the ancient past. These long-lived bodies of water are good indicators that the crater, as well as Mount Sharp within it, were capable of supporting microbial life.

“Early Mars was an extremely active planet from a geological point of view,” Fairén said. “The planet had the conditions needed to support the presence of liquid water on the surface – and on Earth, where there’s water, there’s life.

“So early Mars was a habitable planet,” he said. “Was it inhabited? That’s a question that the next rover Perseverance … will help to answer.”

Perseverance, which launched from Cape Canaveral on July 30, is scheduled to reach Mars on Feb. 18, 2021.


Cornell Chronicle
“This composite, false-color image of Mount Sharp inside Gale crater on Mars shows geologists a changing planetary environment. On Mars, the sky is not blue, but the image was made to resemble Earth so that scientists could distinguish stratification layers. NASA/JPL/Provided” (Cornell Chronicle)

The full text of the excellent paper is available:

Heydari, E., Schroeder, J.F., Calef, F.J. et al. Deposits from giant floods in Gale crater and their implications for the climate of early Mars. Sci Rep 10, 19099 (2020).

As cool as the geology of Gale Crater has been, Jezero Crater promises to be even cooler. Perseverance is about two thirds of the way there and will be an even more capable field geologist than Curiosity has been.

Mars Perseverance rover scientific instruments. (NASA)

Mastcam-Z has powerful cameras that can zoom in, focus, and take color 3-D images and video at high speed to allow detailed examination of distant objects.

MEDA, the Mars environmental dynamics analyzer, is a weather station that measures wind speed and direction, temperature and humidity, and the size and amount of dust particles in the Martian atmosphere.

MOXIE, the Mars oxygen in-situ resource utilization experiment, will demonstrate technology to produce oxygen from the Martian atmosphere for propellant and for breathing air for future human explorers.

PIXL, the planetary instrument for X-ray lithochemistry, is an X-ray spectrometer used to identify chemical composition at a tiny scale. This will allow scientists to look for organic chemicals of possible past microbial life on Mars.

RIMFAX, the radar imager for Mars’ subsurface experiment, is a ground-penetrating radar system that will probe the geology below the rover to a depth of ten meters. RIMFAX will be used to detect ice, water and salty brines.

SHERLOC, the instrument for scanning habitable environments with Raman spectroscopy and luminescence for organics and chemicals, uses spectrometers, a laser and a camera to search for organic chemicals and minerals that may be signs of past microbial life from a wet environment.

SuperCam will examine rocks and soils with a camera, laser and spectrometers to find organic chemicals from possible past life on Mars. It can focus on targets as small as a sand grain from a distance up to seven meters.

Ingenuity UAV helicopter: In addition to this sophisticated instrument suite, Perseverance carries the small UAV helicopter, named Ingenuity, attached to the rover’s belly. It will be deployed for several flights up to 10 meters high and ranging up to 300 meters away from the rover to scout for science targets and driving routes.

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Jeffrey H Kreiley
November 23, 2020 2:37 pm

This is so cool. I love this but am afraid that NASA will be seeing an upcoming drought shortly after January 2021.

Joel O'Bryan(@joelobryan)
Reply to  Jeffrey H Kreiley
November 23, 2020 2:54 pm

Yep, the swamp needs that money for the Climate reparations nd Slave reparations the Democrats have stated they want to dole out. His SecState is a Lobbyist who owns his own lobbying firm in DC. Tell me that ain’t Pay to Play corruption.
Dementia Joe’s putting his old Senate pal Kerry-Lurch-Heinz, Obama’s Paris Deal architect, on his National Security Council to force the Defense Dept to prioritize spending part of its massively large budget chasing Climate unicorns rather than on defending the US and allies from real threats like China. All in all, the Biden-Harris Admin will be a disaster of unprecedented proportions for US national security and that of our allies.

Dementia Joe Biden – Making the Swamp Great Again.

Paul Penrose
Reply to  Joel O'Bryan
November 24, 2020 9:13 am

You mean the Harris-whatever administration. I predict Biden won’t last to the end of 2021. He will either be forced out (using the 25th amendment) or will resign. IMHO

Tom Abbott
Reply to  David Middleton
November 24, 2020 6:39 am

Musk will have to take the lead on the Moon. He is in a position to do so now, if Biden clips NASA’s wings.

Reply to  David Middleton
November 24, 2020 7:39 am


Agreed, David, et al.

This guy who developed a good, reliable workhorse will likely do it on his own. He wants to, and seems “driven” to get to Mars and use Luna on the way. I can also see Bezos getting into the fray.

$50 – $60 per launch is half or less than the price that the “deep state”, entrenched corporations are charging and his outfit has been to the ISS three times with the Crew Dragon while they have yet to get there. And they are being paid lots more than Space X.

Gonna be interesting, the next few years.

Gums sends…

November 23, 2020 2:43 pm

“The planet had the conditions needed to support the presence of liquid water on the surface – and on Earth, where there’s water, there’s life.

And people wonder why SCIENCE™ is no longer taken seriously.

Never mind the decades of endless Crevo discussions.

We are now reduced to univarient equations with binary results: Water = Life.

Joel O'Bryan(@joelobryan)
Reply to  AWG
November 23, 2020 3:03 pm

Yeah that bit hit me too as disingenuous PR to sell to a naive public.
They use an experiment where n = 1 (Earth) to conclude that everywhere there’s liquid water, life must spring up. Anti-science in action.

But I’m all for this robotic exploration stuff of Mars, the asteroids, and the moons of Jupiter and Saturn. The manned stuff for all that Mars stuff ain’t happening if NASA is to stick to its Manned Space Flight risk criteria for mission failure (death of the crew due to radiation exposure) and greatly elevated cancer risk, heart disease risk, and dementia risk for astronauts who manage to the survive a Mars-Earth round trip.

Reply to  Joel O'Bryan
November 23, 2020 5:22 pm

“Jul 19, 2019 — @ElonMusk: Fully Fueled StarShip in orbit carrying 100 tons of cargo will have 6.9km/s of Delta-V. According to this map, 6.9 km/s is enough Delta-V to put the StarShip plus cargo: on the surface of the Moon.”

I think a Fully Fueled StarShip in high Earth orbit {say Earth/Moon L- 1} can get crew to Mars in 3 months. And it seems 2 Fully Fueled StarShips at High Earth orbit, could get to Mars in 3 months and join together, spin, and get artificial gravity for the 3 month journey.
That could result in crew getting less radiation then 6 months at ISS and be better shape by using the artificial gravity.
Before doing that, send 1 starship doing hohmann transfer without crew, to be a return ship to Earth, so Crew getting to Mars fast, could have abort option to return to Earth, waiting them in Mars orbit.
Musk wants to send 100 passenger using starship, but would instead send 6 crew, 3 per starship.
The cost of Crew Mars exploration program should be less than 4 billion dollar per year {a bit more than what NASA has spent on ISS. The crew cost should be about 200 million per per crew per year- 1.2 billion for 6 crew.

Joel O'Bryan(@joelobryan)
Reply to  gbaikie
November 23, 2020 6:21 pm

The Moon is irrelevant. We did that 50 years ago.
Your description a fully fueled Starship at Earth-Moon libration pt utterly lacks the substantial understanding and difficulties of getting large manned vehicles to that point outside of Earth’s protective magnetosheath on a Mars intercept that then has to almost equally decelerate to acquire Mars orbit.
You have NOT identified a design concept for a Mars Descent vehicle, the Mars habitat, nor the Mars ascent vehicle to return the Mars astronauts back to the Starship(s) for the return trip.

Your mission design is not anywhere in NASA’s current Manned Mars Concept and Design.
i.e. Your design is pure fantasy.

Reply to  Joel O'Bryan
November 23, 2020 8:10 pm

“The Moon is irrelevant. We did that 50 years ago.”
The moon might have mineable water in it’s polar regions. Regardless of whether we find mineable water in polar region, the Moon is gateway to rest of solar system. The Moon is not irrelevant, but if the moon doesn’t have mineable water, one could consider the Moon irrelevant in the near term. The Moon could be useful in regards to establishing settlement on Mars, but if Moon is not useful in terms of establishing human settlement on Mars {doesn’t have mineable water}, if we get human settlements on Mars, than the Moon has to become a gateway to solar system.

Or old argument of Moon vs Mars is really about, which should be done first.
I would argue Moon is easier to explore. And we should quickly explore Lunar polar region, and then quickly start exploring Mars. And it could take a long time to explore Mars as there many aspects and has vast amount of land area that needs to be explored enough to determine if Mars settlements could be viable.

“Your description a fully fueled Starship at Earth-Moon libration pt utterly lacks the substantial understanding and difficulties of getting large manned vehicles to that point outside of Earth’s protective magnetosheath on a Mars intercept that then has to almost equally decelerate to acquire Mars orbit.”
Earth/Moon L-1 requires less delta-v than landing on lunar surface, and Earth/Moon L-1 is nearest L-point. Getting to a lunar orbit, requires less delta-v than getting to Geostationary Orbit- and getting lunar orbit is a way to lower the amount of delta-v to get to GEO.
Ie: “On May 13, 1998, the Hughes Global Services 1 Spacecraft (HGS-1, originally known as AsiaSat 3) became the first commercial spacecraft to fly by the Moon on a trajectory to reposition it into a useful geosynchronous orbit. This was necessary due to the failure of the last stage of the launch vehicle that left it in a high inclination, eccentric, and unusable orbit. The spacecraft did not have enough propellant to perform the maneuvers required to place it into its intended geostationary orbit via a standard transfer trajectory. However, it did have enough propellant to place it on a trajectory that flew by the Moon twice to finally achieve a useful low inclination geosynchronous orbit. In addition to being the first commercial operation in the vicinity of the Moon, it was the last successful lunar mission of the twentieth century.”
Anyhow, Earth/Moon L-1 is rough region of Space which is quite large-
There is a mathematic point, but there is no reason to go to that small point in space- one could have various orbits around it. Or any high earth orbit or simply not medium Orbit like GEO. Wiki defines as:
“A high Earth orbit is a geocentric orbit with an altitude entirely above that of a geosynchronous orbit (35,786 kilometres (22,236 mi))”

And what I mean by high earth orbit, is orbit which doesn’t require much delta-v to make fall towards earth, and becoming a highly elliptical orbit with a low earth orbital distance as it’s perigee. And it’s at this perigee, where uses the delta-v of rocket thrust to go to Mars.
So any high orbit or it just be a highly elliptical orbit with apogee reaching high earth orbit distance- like say, 100,000 km or more apogee distance from Earth. Or also one could say all 10 of Earth L-points are the highest Earth orbits {which are somewhat stable or require little in terms of station keeping}.

Beta Blocker
Reply to  David Middleton
November 23, 2020 4:15 pm

David, do you have a link to a science article that in your opinion best describes and explains the origin and subsequent evolution of life on earth? Is an earth-like planetary position relative to the star a planet orbits around an essential element of the very initial origins of life?

Ron Long
Reply to  David Middleton
November 23, 2020 5:50 pm

Besides, we already know there was life on Mars. Remember Otis Sistrunk? Played on the Oakland Raiders? He claimed he was from the University of Mars, and I remember John Madden agreeing. I don’t mean to be racist, but the video of Otis on the sidelines without his helmet and the steam rising off his head lends some credence to his claim.

John Tillman
Reply to  Beta Blocker
November 24, 2020 6:53 am

Life could still develop on a planet or moon outside the habitable zone (with liquid water on the surface), given an energy source besides the Sun, such as gravitational flexing or from internal heat.

The presently two leading candidates for the incubator of life on Earth are certain deep sea vents and volcanic ponds on land. The buiklding blocks of life–sugars, nucleic, amino and fatty acids–arise spontaneously on Earth and in outer space. The trick to life is getting the monomers and oligomers of these chemical compound constituents to polymerize and replicate.

Great advances have been made in origin of life research since the 1950s.

Clyde Spencer
Reply to  David Middleton
November 23, 2020 5:11 pm

Yes, Earth is “the only example we have to go by. Thus, we can be fairly confident that in the absence of water, we are unlikely to find Earth-like life. However, we have sufficient understanding of chemistry to speculate that something like liquid ammonia might serve the role of universal solvent necessary for biological organisms to evolve and thrive. There may yet be Black Swans to be found.

Reply to  AWG
November 23, 2020 3:28 pm


Reply to  AWG
November 23, 2020 4:17 pm

Don’t be so cranky, it’s probably a typical condition for life, but I won’t be surprised if life is found growing in the molten sulfur lakes on Io or under the surface of the north pole of the moon.

Bill Parsons
November 23, 2020 3:26 pm

Looks like Navajo country badlands, any number of places. Here the Petrified Forest National Park.

A dykstra
November 23, 2020 3:44 pm

Planetary flood where there is no water but impossible on earth where there is plenty of water. Go figure.

Joel O'Bryan(@joelobryan)
Reply to  David Middleton
November 23, 2020 6:55 pm

“and the animals, birds, and beasts went two by two into the Ark.”
If only we could rid ourselves of Democrats so easily.

Ric Werme(@ricwerme)
Reply to  A dykstra
November 23, 2020 10:19 pm

The floods in the Pacific Northwest from the repeated drainings of Lake Missoula at the end of the last glaciation left obvious scars and whatnot between Montana and Washington. The evidence of those floods was used to support the notion of huge floods on Mars.

When I bicycled through Missoula in 1974, I thought the hills around Missoula were oddly shaped and vegetated. A new months later an aerial photo of the hill I hiked up was featured on the cover of Science News.

Not only is it entirely possible on Earth, but it has happened, multiple times.

John Tillman
Reply to  A dykstra
November 24, 2020 9:10 am

The Martian megaflood wasn’t planetary. Mars used to have surface water, when its atmopshere was denser and it had a magnetosphere.

John Tillman
Reply to  John Tillman
November 24, 2020 12:41 pm

It’s a kind of jökulhlaup, the Icelandic term for a glacial outwash flood. In this case rather than a glacier, the ice was possibly frozen in the ground rather than on it.

John Tillman
Reply to  A dykstra
November 24, 2020 12:51 pm

The Gale Crater megaflood wasn’t planetary, but a regional jökulhlaup.

Noah’s Flood would have required 3.5 times all Earth’s seawater. Whence came these mythical waters 4500 years ago and where did they go?

November 23, 2020 3:45 pm

“where there’s water, there’s life”

Empirical evidence for the claim that water is a sufficient condition for life to originate on a planet in a habitable zone?

John Endicott
Reply to  Ralph Dave Westfall
November 24, 2020 9:54 am

Ralph, you sniped an important contextual phrase from that quote “and on Earth, “. It’s merely an observation based on what we’ve seen here on Earth and flagged as such. It’s not the statement of a universal absolute that you are disingenuously trying to paint it out to be.

November 23, 2020 3:55 pm

Mars is too harsh for life larger than microbes. But isn’t it also possible that a planet with an ideal climate for its developed life forms might never evolve what we call “intelligent” life, as there would be no need to compete for success. Sorta maxing out at whales, with whom we cannot have an intelligent exchange of ideas, despite their large brain size, although their songs are more musical than rap….

Bryan A
Reply to  DMacKenzie
November 23, 2020 7:17 pm

A rubber band pulled taught between two fingers and twanged at differing stretches is more muscle than (c)Rap
Shoot, my gramps blowing his nose is more muscle than (c)Rap

Richard Aubrey
November 23, 2020 3:57 pm

Any of them like, really straight?

Any beauty, calm, and south?

Geoff Sherrington
November 23, 2020 5:59 pm

Oldest life so far on Earth is about 3.5 billion years. Water on Mars at 5 billion might not have been relevant if gone again. Sadly, we are far from knowing all of the conditions required before Life starts anywhere. Maybe this can be called the greatest known mystery.
Geoff S

John Tillman
Reply to  Geoff Sherrington
November 24, 2020 6:45 am

There is controversial evidence for life on Earth possibly as far back as 4.29 Ga.

November 23, 2020 6:58 pm

I seems to me that it is possible, that Mars has more life than Earth has.



Life Thrives Within the Earth’s Crust
HomeArchiveOctober 2018Features
Life Thrives Within the Earth’s Crust
From journeys into mines to explorations of volcanoes on the ocean floor, deep voyages reveal the richness of the planet’s deep biosphere.
Catherine Offord
Catherine Offord
Sep 30, 2018
About a 20-minute drive north of the industrial town of Timmins, Ontario, the ground gives way to a gaping pit stretching more than 100 meters across. This pit is the most recognizable feature of Kidd Creek Mine, the deepest copper and zinc mine in the world. Below the Earth’s surface, a maze of underground tunnels and shafts pierces 3 kilometers of ancient volcanic rock. Were it not for a huge ventilation system keeping the passages cool, the air temperature at this depth would be 34 °C (93 °F).

It’s here that Barbara Sherwood Lollar, a hydrogeologist at the University of Toronto, journeys into the planet’s crust to hunt for signs of life. “You get into a small truck or vehicle and go down a long, winding roadway that corkscrews down into the Earth,” she tells The Scientist. By the time she and her fellow passengers clamber out into the corridors at the end of the roadway, “we are literally walking along what was the ocean floor 2.7 billion years ago,” she says. “It’s an utterly fascinating and magical place to visit.”

Unlike miners, who navigate these tunnels in search of metal ores, Sherwood Lollar and her colleagues are on the lookout for pools of salty water. “These aren’t waters you’d pump into your cottage and drink or spread on your crops,” Sherwood Lollar says. “These are waters that have been in contact with the rock for long geochemical timescales—they’re full of dissolved cations and anions that they’ve leached out of the minerals.” So full, in fact, that they give off a distinctive, musty odor. “As we’re walking along these tunnels, if I get a whiff of that stenchy smell, then we head in that direction.”

Where there’s water, there’s the potential for life. In 2006, Sherwood Lollar was part of a team led by Tullis Onstott at Princeton University that discovered an anaerobic, sulfate-reducing bacterium thriving in the sulfate-rich fracture waters of Mponeng gold mine in South Africa, 2.8 kilometers underground.1 A few years later, a different group described a diverse microbial community living at a similar depth in the Earth’s crust, accessed via a borehole drilled into the ground in Finland.2 With the recent discovery of 2-billion-year-old, hydrogen- and sulfate-rich water seeping out of the rock in Kidd Mine, Sherwood Lollar and her colleagues are hoping they might again find life.3

Before the rise of the land plants, deep biomass could have outweighed life on the surface by an order of magnitude.

These expeditions are just one part of a rapidly expanding field of research focused on documenting microbial and even eukaryotic life dwelling hundreds of meters deep in the Earth’s crust—the vast sheath of rock encasing the planet’s mantle. Researchers are now exploring this living underworld, or deep biosphere, not only in the ancient, slow-changing continental crust beneath our feet, but in the thinner, more dynamic oceanic crust under the seafloor. (See illustration on page 32.) Such habitats have become more accessible thanks to the last two decades’ expansion of scientific drilling projects—whereby researchers haul up cores of rock to study on the surface—as well as a growing number of expeditions into the Earth via mines or cracks in the ocean floor.

Studies of these dark—and often anoxic and hot—environments are challenging scientists to rethink the limits of life, at the same time highlighting how little we know about the world beneath our feet. “It’s a really good field if you don’t mind not knowing all the answers,” says Jason Sylvan, a geomicrobiologist at Texas A&M University. “For some people, that freaks them out. For me, a field is more exciting when you can ask really big questions.”

Researchers Explore the Deep Biosphere
Most research into the deep biosphere has been conducted using samples retrieved from less than a kilometer below the surface of the Earth. But a handful of boreholes and other manmade excavations at both continental and oceanic sites extend much deeper into the Earth’s crust.

Numbers 1-10: West to East.

Location Depth About
1 Hole 1256D,
East Pacific Ocean 1.5 km Researchers reported evidence of microbially produced sulfides at this site in 2011.
2 Kidd Creek Mine,
Canada 3.0 km In billions-of-years-old water samples, researchers found sulfate produced by interactions between water and rock, suggesting that any microbes living there would have an easily available food source.
3 Hole 504B, Costa Rica Rift 2.1 km Analysis of carbon isotopes in the 1990s suggested microbial activity, while a more recent analysis of data collected from an observatory in a shallower hole about a kilometer away revealed sulfur-oxidizing bacteria.
4 Hole U1309D,
Atlantis Massif 1.4 km In 2010, researchers reported the presence of a community of bacteria surviving at depths of more than 1.3 kilometers, apparently surviving by degrading hydrocarbons and fixing carbon and nitrogen in the absence of oxygen.
5 KTB Boreholes,
Germany 9.1 km Temperatures at the base of the deepest well at this site reach 265°C—the most hyperthermophilic organisms known on anywhere on the planet can only survive to 113°C—and life has not yet been reported here.
6 St1 Otaniemi,
Finland 9.1 km Temperatures at the base of the deepest well at this site reach 265°C—the most hyperthermophilic organisms known on anywhere on the planet can only survive to 113°C—and life has not yet been reported here.
7 Mponeng gold mine,
South Africa 3.9 km In the mid-2000s, researchers identified a new species of sulfate-reducing bacteria, Candidatus Desulforudis audaxviator, that seems to be endemic to deep habitats.
8 Kola superdeep borehole,
Russia 12.3 km Researchers reported finding water and microscopic fossils of single-celled organisms more than 6 kilometers below the surface.
9 Hole 735B Southwest,
Indian Ridge 1.5 km In 2011, an isotope analysis of samples revealed evidence that seawater sulfate was being chemically reduced by microbes.
10 Hole C0020A,
Japan Sea 2.5 km Early results indicate a slow-growing microbial community able to metabolize a range of carbon and nitrogen compounds more than 2 km below the seafloor.

Holes in the ground
A desire to explore the deep biosphere has led Julie Huber, a microbial oceanographer at Woods Hole Oceanographic Institution in Massachusetts, to some of the remotest places on Earth. Huber is interested in the huge volumes of water swilling around between rock particles in the oceanic crust, and the extent and diversity of microbial life within them. One way to access that water is via expensive drilling projects, many organized by the International Ocean Discovery Program (IODP), that bore through marine sediments to the crust. In 2013, this approach revealed bacteria living in 3.5-million-year-old basalt rock underneath the Pacific Ocean.4

The other way, Huber explains, “is to find where that water is naturally leaking out through the seafloor, and then try to capture it just as it’s coming out.” For that purpose, Huber has not only worked with teams of engineers to guide remotely operated vehicles down to the bottom of the ocean, she’s also joined the ranks of scientists who have taken the plunge with Alvin, a three-person submersible research vehicle owned by the US Navy that can dive down as far as 4,500 meters. “Claustrophobic people don’t do well in there,” Huber acknowledges—adding that anyone planning to dive is invited to try sitting in the sub before it leaves the boat deck to avoid “a full-on panic being launched into the ocean.”

Mines offer researchers direct access to the deep biosphere, kilometers into the Earth’s continental crust. Scientists have now used several of these sites, from Kidd Creek Mine in Ontario (left) to gold mines in South Africa (right), to search for underground life.
These technologies allow Huber to collect samples of the fluids seeping, or sometimes exploding, out of the oceanic crust from underwater volcanoes and hydrothermal vents. In the early 2000s, she and her colleagues used 16S rRNA gene sequencing to analyze subseafloor microbial diversity following multiple eruptions of Axial Seamount, an underwater volcano about 480 kilometers west of Oregon and nearly 1.5 kilometers under the water’s surface. Compared to background seawater, samples collected at the vent site revealed multiple unique bacterial5 and archaeal6 taxa that appeared to have been blasted out of the crust, pointing to a diverse microbial community thriving below the seafloor. More recently, Huber’s group carried out a detailed survey at the world’s deepest hydrothermal vent field—a site known as Piccard, after Swiss deep-sea adventurer Jacques Piccard—and turned up thousands of vent-specific microbial taxa in fluids exiting the crust at temperatures of up to 108 °C (226 °F).7

Such findings are becoming typical of this young research field. To date, studies of crustal sites all over the world—both oceanic and continental—have documented all sorts of organisms getting by in environments that, until recently, were deemed inhospitable, with some theoretical estimates now suggesting life might survive at least 10 kilometers into the crust. And the deep biosphere doesn’t just comprise bacteria and archaea, as once thought; researchers now know that the subsurface contains various fungal species,8 and even the occasional animal. Following the 2011 discovery of nematode worms in a South African gold mine, an intensive two-year survey turned up members of four invertebrate phyla—flatworms, rotifers, segmented worms, and arthropods—living 1.4 kilometers below the Earth’s surface.9

Jules Verne enthralls readers with a story of underground seas and prehistoric animals in his subterranean sci-fi, Journey to the Center of the Earth.

Geologist Edson Bastin and microbiologist Frank Greer of the University of Chicago report finding sulfate-reducing bacteria in samples retrieved from 300- million-year-old oil deposits that were buried hundreds of meters underground. The results are dismissed as surface contamination.

Microbiologist Claude Zobell describes aerobic bacteria in cores more than 50 centimeters long taken from deep-sea marine sediments off the coast of California, leading to speculation about life below the seabed.

Ocean explorer Jacques Piccard discovers animal life at the deepest known point in the ocean, Challenger Deep in the Mariana Trench, nearly 11 kilometers beneath the surface of the water.

US Department of Energy engineers using drilling equipment designed to avoid surface contamination discover microbes living 500 meters underground around a nuclear processing facility near the Savannah River in South Carolina.

Astrophysicist Thomas Gold publishes an influential, controversial paper entitled “The Deep, Hot Biosphere,” arguing that subsurface biomass is comparable in volume to surface biomass, and that life may have originated underground.

Researchers discover a bacterium in fracture waters in a South African gold mine, 2.8 kilometers underground. Subsequent work shows it has no close relatives on the surface.

An ocean drilling program retrieves microbe-containing basalt, providing the first conclusive evidence of life in the oceanic crust.

Japanese researchers announce plans to drill all the way through the Earth’s crust to the mantle. The project, slated to start by 2030, is partly aimed to help answer the lingering question of how deep underground life can survive.

Unsurprisingly, as researchers explore these unusual habitats, they’re finding a number of organisms that were until recently unknown to science. The discovery of “extremophile” archaea species in the last decade has led scientists to rethink the entire domain’s phylogeny. (See “Archaea Family Tree Blossoms, Thanks to Genomics,” The Scientist, June 2018.) And while many of the bacteria and archaea discovered in the deep biosphere have analogs or close relatives on the surface, some are unlike anything found anywhere else.

One example is Candidatus Desulforudis audaxviator, first found by Onstott’s team in Mponeng gold mine in 2006. (“Audax viator,” which translates from Latin to “bold traveler,” is a reference to a line in Jules Verne’s Journey to the Center of the Earth.) Researchers have since identified bacteria resembling this species in other sites a kilometer or more into the crust, but haven’t yet found any close relatives in surface communities. Another bacterial species, unearthed more than 1,000 meters down in the Henderson molybdenum mine in Colorado, shows faint phylogenetic links to members of the phylum Nitrospirae, but is otherwise unlike anything on the surface.10

A key area of research now is understanding how such life survives. Devoid of sunlight, “these systems are typically energy-poor,” says Sherwood Lollar. Compared to surface communities, microbes in the deep biosphere are thought to be relatively slow-growing and sparsely distributed, she adds. While surface soil may contain in excess of 10 billion microbes per gram, oceanic crust usually contains around 10,000 cells per gram, and continental crust—where water is unsurprisingly in shorter supply—holds fewer than 1,000 cells per gram.

Click to watch a video about some of the deepest holes scientists have drilled into the Earth’s crust.
Working with such low-biomass samples presents a challenge of its own, but researchers are using a combination of techniques, including metagenomic analyses and incubation of subsurface rocks or fluids with different potential food sources in the lab, to probe the function of subsurface microbes. Such studies are revealing genes for metabolic enzymes that suggest these organisms can gain energy from a suite of sources—particularly hydrogen and other molecules that are released by chemical reactions between water and rock. When geomicrobiologist Lotta Purkamo of the University of St Andrews and her colleagues characterized the ecosystem of a 600-meter-deep borehole in northern Finland, for example, they found evidence of metabolic pathways based on reducing or oxidizing sulfate, nitrate, methane, ammonia, and iron, as well as fixation reactions involving carbon.11

Additionally, thanks to metatranscriptomic analyses, “we’re learning that these organisms have a lot of potential metabolisms that they could be expressing,” says Huber, who recently carried out this sort of assay on the Axial Seamount community.12 “But depending on the conditions and the geological setting, just a small subset of those genes are being used.” Such results hint at flexible and opportunistic lifestyles, she adds, where microbes make use of whatever they can, whenever they can.

These findings are chipping away at some of the big questions about the diversity and uniqueness of life in the deep biosphere. But the insights afforded by a single drill core or fluid sample can be frustratingly fleeting, says University of Bergen geobiologist Steffen Jørgensen. One sample “doesn’t give us any understanding of the dynamics of the system and how it evolves over time,” he says. For a longer-term view of life deep in the Earth, researchers are taking their experiments underground.

The fourth dimension
Last summer, Jørgensen stepped out of a helicopter onto a tiny basalt island about 30 kilometers from the south coast of Iceland. Too rocky to access by boat, the island of Surtsey is the tip of a huge mound of magma blown out of the seafloor by an under-water volcanic eruption that went on for nearly four years in the mid-1960s. This newly formed oceanic crust “gives us a huge advantage,” Jørgensen says. “We can actually drill into what is a marine system, but from land.”

Using equipment flown to Surtsey by helicopter, Jørgensen and a large team of engineers drilled down into the basalt. They didn’t just remove cores from the island; rather, the researchers set up a mini observatory to take in situ measurements of the deep biosphere. Into a 190-meter-deep hole in the rock, the team installed a series of 10-meter-long aluminum tubes, several with a number of small slits to allow fluids to trickle through from the surrounding rock. Then, into the tubes the team lowered a cable with various bits of equipment—temperature and pressure loggers, and microbial incubators—attached at specific intervals, until the equipment lined up with the slits. Since then, the instruments in the observatory have been collecting data from the oceanic crust, and next summer, Jørgensen and his colleagues will go back to see what they’ve found.

The Surtsey installation is now one of a handful of deep observatories around the world and part of a larger effort to establish long-term studies in both oceanic and continental crust. Such sites offer a window into the activity of the deep biosphere, as well as an opportunity to collect time-series data that are critical to understand how that biosphere changes over time. “It’s the only way that we can . . . make observations that are more than ‘I went to this place, one time in the history of the world, and I grabbed a bunch of rocks, and here’s what I saw,’” says Sylvan.

Journey to the Center of the Earth
The recent expansion of large-scale scientific drilling programs, combined with intensified efforts to take advantage of existing portals into the crust, has led to an explosion of research on the deep biosphere.

Deep-sea, manned submersibles and remotely operated vehicles collect fluid samples that exit natural points of access to the oceanic crust, such as underwater volcanoes or hydrothermal vents. These samples contain microbes living in the crust beneath.

Drilling holes into the Earth’s crust allows retrieval of rock and sediment cores reaching kilometers below the surface. The holes can then be filled with monitoring equipment to make long-term measurements of the deep biosphere.

Deep mines provide access points for researchers to journey into the Earth’s continental crust, from where they can drill even deeper into the ground or search for microbes living in water seeping directly out of the rock.

See full infographic: WEB | PDF

Oceanic Crust Continental Crust
Thickness 6–10 kilometers 30–50 kilometers
Area About 60 percent of Earth’s surface About 40 percent of Earth’s surface
Rarely more than 200 million years Up to 4 billion years
Water Content High Low
Data coming out of long-term studies of the deep biosphere paint a dynamic picture. This July, a team that included Onstott and Sherwood Lollar published metagenomic, metatranscriptomic, and metaproteomic analyses of data collected over a period of two and a half years at a depth of 1,339 meters from a borehole drilled into South Africa’s Beatrix gold mine.13 Over the course of the study, the microbial community structure shifted in concert with natural fluctuations in the groundwater’s geochemistry—in particular, the availability of electron-accepting compounds such as nitrates and sulfates.

Meanwhile, Huber’s group published an analysis of data gathered over two years from two so-called CORK (circulation obviation retrofit kits) observatories installed in the oceanic crust below North Pond, a site on the Mid-Atlantic Ridge, through which circulates well-oxygenated and—at less than 15 °C (59 °F)—relatively cold water.14 Metagenomics showed that the microbial communities, which were substantially different from those of warmer and anoxic environments, went through substantial shifts over time—with one phylum dominating one month, and another taking over the next—despite only minor fluctuations in the water’s geochemistry.

Such underground observatories can also act as in situ laboratories. By incubating rocks inside these sites for years at a time, researchers can study how microbial communities colonize new material in their natural environments rather than in the lab, and how the mineralogical composition of the crust influences who grows where.15 The sites might even reveal subsurface dynamics on much longer timescales, by helping scientists identify signs of ancient life. To date, many of the clues about deep microbial communities throughout geological history come from what look like fossilized or mineralized remains of bacteria and archaea on rocks retrieved from the crust. But given how little researchers know about the processes of mineralization in the deep subsurface, the authenticity of at least some of these remains is in question.

“It’s quite difficult to tell whether you’re actually looking at a fossil of an organism that lived in the deep biosphere billions of years ago,” explains University of Edinburgh geobiologist Sean McMahon. “Not only is it difficult in general to recognize fossil bacteria, which look very much like minerals at that size scale, it’s difficult to show, if it really is a fossil bacterium, that the organism lived below the surface at the time it was living billions of years ago.”

It’s a really good field if you don’t mind not knowing all the answers.

—Jason Sylvan, Texas A&M University
To get a better grip on the long-term dynamics of the deep biosphere, groups such as McMahon’s are trying to recreate deep mineralization in the lab. They do this by inoculating rocks with bacteria, McMahon explains, then tweaking physical and chemical conditions to trigger fossilization. “The idea is to try and find the sweet spot where the microbes are able to live happily, but you only have to change a small thing for them to become entombed in minerals and fossilized,” he says.

Underground observation stations such as the one at Surtsey will soon be able to complement this research, says Jørgensen. “By having the observatory, we can hopefully clarify whether these [fossil-like] structures can be produced abiotically, or if we only see them where there’s microbes present,” he says. “It is a very difficult question to get to the bottom of.”

The Icelandic island of Surtsey (left) was created by a four-year volcanic eruption in the 1960s.

Researchers have now installed a deep observatory into a hole they drilled to monitor life in the deep marine biosphere.
Missing pieces
Despite the infancy of research into the deep biosphere, it’s clear to many in the field that science has long held a warped view of what constitutes life in our universe. Researchers are far from agreeing on the extent of this underworld—one 1990s paper controversially suggested that deep life constituted 50 percent of the Earth’s current biomass,16 though most estimates are now below 15 percent. Before the rise of land plants around 400 million years ago, though, deep biomass could have outweighed life on the surface by an order of magnitude, according to calculations published this summer by McMahon and the University of Aberdeen’s John Parnell.–

John Endicott
Reply to  gbaikie
November 25, 2020 9:22 am

Given the results of the recent US election, it’s quite possible that Mars has more Intelligent life then on this big blue marble. 😉

Robert of Texas
November 23, 2020 7:03 pm

Water does NOT equal “evolution of life”. There was already the possibility of life having evolved on Mars, no matter how slight a chance, and this really does not change that. A nice stable pool of warm water with nutrients in it to make amino acids would suffice.

I think at least as important to the evolution of life is some amount of stability. It’s hard to get started when the rug keeps getting pulled from underneath you. Mars had at best a weaker magnetic field, no stabilizing moon, and likely lost and plate tectonics it might have had early on.

Unlikely but still possible is that life jumped from Earth to Mars early on through a asteroid impact. I say unlikely because the life form would have had to survive outer space for years, survived a violent toss from Earth, and have had a path that got it outward to Mars. Not impossible. Not likely.

I guess I have become a pessimist over the years on us ever discovering life beyond the Earth. I think its rare enough not to have happened in our solar system except for Earth, and there just is no reasonable path to discovering it in other star systems in our lifetimes. I hope I am wrong, but think that I am right.

John Tillman
Reply to  Robert of Texas
November 24, 2020 7:02 am

Mars’ surface probably cooled sooner than Earth’s, so life might have gotten started there before here.

I may be too optimistic, but I’d rate the odds of past life on Mars at over 50:50, and for its still being there at under, but by no means highly improbable.

November 23, 2020 7:39 pm

Capable field Geo? I didn’t see a pack of coloured pencils anywhere.

Let the rivalry between Geos and Mining engineers continue in space!

Reply to  David Middleton
November 23, 2020 9:02 pm

I haven’t looked at any textbook from my early ’80s uni days in the last 20 years, but still use my Estwing regularly

November 23, 2020 9:09 pm

All the fault of ancient Martians generating too much CO2, I’m sure.

November 23, 2020 9:53 pm

Same problem as all the other so called ‘water phenomenon’ on Mars; gas, sand and fluidised rock currents can all produce the same appearance of sedimentological effects as water does. Rounded pebbles can be produced by simply rolling dry rocks around, for example, something that would be expected from either volcanism, which is known on Mars, or by bolide impacts. And there is another explanation, the known Martian volcanism might be expected to produce hot hydrothermal fluids, but these would not last longer than the volcano.

November 24, 2020 1:09 am

If there was water on Mars, where did it come from? How long did it last? where did it go?

Reply to  David Middleton
November 24, 2020 7:01 am

“As cool as the geology of Gale Crater has been, Jezero Crater promises to BE even cooler. “

Reply to  Roger
November 24, 2020 10:25 pm

Heck! We haven’t really figured out where all this water we have on earth came from yet! The arguments go on. But I seriously doubt the theory that most of it came from comets.

November 24, 2020 5:03 am

So CO2 got the martians too? Gulp!

Tom Abbott
November 24, 2020 7:05 am

From the article: ““Deposits left behind by megafloods had not been previously identified with orbiter data.”

We need boots on the ground, David! 🙂

From the article: “The most likely cause of the Mars flooding was the melting of ice from heat generated by a large impact, which released carbon dioxide and methane from the planet’s frozen reservoirs. The water vapor and release of gases combined to produce a short period of warm and wet conditions on the red planet.”

There’s that hottie carbon dioxide! It looks like it’s increased concentration in the atmosphere is following temperature increases, even on Mars. What a coincidence. That’s the way it works on Earth, too, although it doesn’t take a comet strike or volcanic eruption on Earth, just a planet-wide ocean, and input from the Sun, to raise and lower the CO2 concentrations in the atmosphere.

The thin atmosphere of Mars is almost all CO2 now. No oceans on Mars to absorb CO2, although some CO2 freezes out onto the surface.

John Endicott
Reply to  Tom Abbott
November 25, 2020 9:24 am

We need boots on the ground

Elon’s working on it.

November 24, 2020 8:38 am

Nothing like having a first hand look. Good to know people are working on it.

November 26, 2020 12:56 pm


I do not unnerstan why Mars is not boiling hot.

Maybe one day soon a reporter will ask John Kerry about this…

” Sir, science tells us ‘The thin atmosphere of Mars is almost all CO2 now.’ If all our autos and trains and planes are emitting lottsa carbon dioxide, then why is it so cold on Mars?”

Gums ponders…

william elbel
December 4, 2020 4:28 pm

Maxwell-Boltzmann predicted that nearly all Martian surface water and water vapor would have escaped into outer space in less than 10,000,000 earth years, since the Martian velocity distribution of water vapor molecules overlaps the escape velocity for Mars which is lower than Earth because of the much smaller than Earth planetary radius.

This escape into space of water vapor is further assisted by the “solar wind.”

The gigantic water flow mentioned would be restricted to those 10,000,000 earth years

Any Martian polar water ice, however sublimates at a much slower rate than expected due to the Martian dust cover.

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