Hydrogen-fed bacteria may exist beyond Earth
NASA-ARC NEWS RELEASE
Posted: April 4, 2002

Primitive bacteria exist in huge numbers deep in the Earth, living on hydrogen gas produced in rocks, a NASA scientist reports in the spring issue of the journal Astrobiology.

Recent studies suggest that the mass of bacteria existing below ground may be larger than the mass of all living things at the Earth's surface, according to recent studies cited by the paper's lead author, Friedemann Freund, who works at NASA Ames Research Center in California's Silicon Valley. Similar hydrogen-consuming microbes may some day be discovered on Mars, raising new prospects for the possible existence of life beyond Earth, Freund added.

"The hydrogen that could feed bacteria in the depth of the Earth comes from a subtle chemical reaction that occurs within rocks that were once hot or even molten. In the top 20 kilometers (12.4 miles) of Earth's crust," Freund said, "the conditions are right to produce a nearly inexhaustible supply of hydrogen. In the top 5 to10 kilometers (about 3 to 6 miles) all fissures and cracks in the rocks are probably filled with water. Hydrogen molecules will seep out of the mineral grains, enter the intergranular space and saturate the water. Microorganisms that live in these water films can be expected to use this hydrogen as their vital energy source."

Many of the microorganisms in the 'deep biosphere' do not live off the sunlight-derived energy that green plants trap during photosynthesis, but live on chemically derived energy sources such as hydrogen, according to Freund. "If deep microbial communities are to thrive over long periods of time, they need a steady supply of hydrogen," he said.

It has long been known that hydrogen gas is produced when water reaches freshly formed cracks in many common rocks, but Freund's paper describes a different hydrogen-producing reaction that occurs inside the minerals that make up such rocks. This reaction does not require rocks to crack - a necessarily episodic event. Instead, it occurs in the entire rock volume during its gradual cooling as continents slowly age over millions of years. Because the Earth's crust contains a huge quantity of rock, even a small amount of hydrogen produced in each small section of rock results in a large volume of gas.

To understand the details of this hydrogen-producing reaction, Freund said, requires some insight into the structure of minerals where silicon, oxygen and metals have combined to form a dense pack of atoms and ions. When these minerals crystallize at high temperatures, water is always present, and some water molecules are trapped in the atomic structure of the minerals, said Freund. These water molecules are ripped apart and change into hydroxyl anions, each of which is negatively charged and has one oxygen ion with a proton attached.

"During cooling, at temperatures below 400 to 500 degrees C (752 to 932 degrees F), a strange reaction takes place. Pairs of these hydroxyl anions rearrange their electrons in such a way that hydrogen gas molecules are formed," Freund said.

What is unusual and still not fully understood, said Freund, is that the electrons needed to make the hydrogen molecules are taken away from negatively charged oxygen anions. "Suddenly, some oxygen anions, which everybody thought only existed in a doubly charged negative state, convert to singly charged negative ions," he said. "These single negative oxygen anions join in pairs. In this form, they are innocuous and can stay inactive over geological times." The hydrogen molecules, however, wander around inside the mineral structure and can squeeze into the narrow spaces between the mineral grains. If the intergranular space is filled with water, the hydrogen molecules will dissolve in the water. If microbes live in the intergranular water films, one can imagine, said Freund, that these bacteria extract the dissolved hydrogen from the water and use this hydrogen as an energy source, not unlike fish that extract oxygen dissolved in the water of rivers, lakes and the sea to respire.

"What is potentially important," Freund said, "is that, if and when microorganisms in the deep underground use this hydrogen dissolved in the intergranular water films, the rocks around them will replenish the hydrogen supply - indefinitely, over eons of time."

The paper by Freund and his coworkers also may help answer non-biological questions related to the commercial viability of tapping hydrogen reserves deep in the rocks and to questions of mine safety. For example, sometimes, during mining and drilling operations, enough hydrogen seeps out of wall rocks that explosive gas mixtures can be produced, according to some reports.

"Since old, old times, the mining industry has had its share of mine explosions in which hydrogen played a role," Freund said, "but hydrogen gas could also be used as an energy source and fuel in today's or tomorrow's society. For years, pipelines have been distributing hydrogen gas between different industrial partners in the Ruhr Valley in Germany, and the experts say it can be handled about as safely as natural gas."

Women Astronauts
Learn about women astronauts,what they do, and how they got to where they are today. Read their story and how attitudes towards women in space changed.
 U.S. STORE
 WORLDWIDE STORE

Apollo 11 special patch
Special collectors' patch marking the 35th anniversary of the historic Apollo 11 moon landing is now available.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Inside Apollo mission control
An insider's view of how Apollo flight controllers operated and just what they faced when events were crucial.
 Choose your store:
U.S.

The ultimate Apollo 11 DVD
This exceptional chronicle of the historic Apollo 11 lunar landing mission features new digital transfers of film and television coverage unmatched by any other.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Next ISS crew
Own a little piece of history with this official patch for the International Space Station's Expedition 11 crew. We'll ship yours today!
 Choose your store:
U.S.

Apollo 12 tribute DVD set

New! Featuring the jovial crew of Pete Conrad, Dick Gordon and Alan Bean, the Apollo 12 mission was struck by lightning shortly after liftoff but proceeded on the second successful exploration voyage to the lunar surface. This three-disc DVD brings the mission to life with extraordinary detail.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Fallen Heroes special patch
This special 12-inch embroidered patch commemorates the U.S. astronauts who made the ultimate sacrifice, honoring the crews of Apollo 1, Challenger and Columbia.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Women in Space
Women of Space: Cool Careers on the Final Frontier is for girls, young women, and anyone else interested in learning about exciting careers in space exploration. Includes CD-ROM.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Mars rover poster
This new poster features some of the best pictures from NASA's amazing Mars Exploration Rovers Spirit and Opportunity.
 Choose your store:
U.S.

STS-134 Patch

Free shipping to U.S. addresses!

The final planned flight of space shuttle Endeavour is symbolized in the official embroidered crew patch for STS-134. Available in our store!
 U.S. STORE
 WORLDWIDE STORE

Final Shuttle Mission Patch

Free shipping to U.S. addresses!

The crew emblem for the final space shuttle mission is now available in our store. Get this piece of history!
 U.S. STORE
 WORLDWIDE STORE

Apollo Collage
This beautiful one piece set features the Apollo program emblem surrounded by the individual mission logos.
 U.S. STORE

STS-133 Patch

Free shipping to U.S. addresses!

The final planned flight of space shuttle Discovery is symbolized in the official embroidered crew patch for STS-133. Available in our store!
 U.S. STORE
 WORLDWIDE STORE

Anniversary Shuttle Patch

Free shipping to U.S. addresses!

This embroidered patch commemorates the 30th anniversary of the Space Shuttle Program. The design features the space shuttle Columbia's historic maiden flight of April 12, 1981.
 U.S. STORE
 WORLDWIDE STORE

Mercury anniversary

Free shipping to U.S. addresses!


Celebrate the 50th anniversary of Alan Shephard's historic Mercury mission with this collectors' item, the official commemorative embroidered patch.
 U.S. STORE
 WORLDWIDE STORE

Fallen Heroes Patch Collection
The official patches from Apollo 1, the shuttle Challenger and Columbia crews are available in the store.
 U.S. STORE
 WORLDWIDE STORE

Hubble Posters
Stunning posters featuring images from the Hubble Space Telescope and world-renowned astrophotographer David Malin are now available from the Astronomy Now Store.
 U.S. STORE
 U.K. & WORLDWIDE STORE

Get e-mail updates
Sign up for our NewsAlert service and have the latest news in astronomy and space e-mailed direct to your desktop (privacy note: your e-mail address will not be used for any other purpose).
Enter your e-mail address:

INDEX | PLUS | NEWS ARCHIVE | LAUNCH SCHEDULE
ASTRONOMY NOW | STORE

ADVERTISE

© 2012 Spaceflight Now Inc.