By: Jeanna Bryner, LiveScience Managing Editor
Published: 08/08/2012 08:07 AM EDT on LiveScience
The region beneath Earth's surface may be crawling with diverse organisms, and now researchers reveal the lives of just one group of bizarre beasties: methane-spewing microbes that hide out in the cracks of hot undersea volcanoes.
Called high-temperature methanogens, these microbes rely on the hydrogen and carbon dioxide in their superheated deep-sea vents for growth, excreting waste products like methane.
The possibility of past or present life on other worlds such as Mars, where the rover Curiosity has just set out to investigate whether the environment was ever fit for microbes, will become clearer by figuring out the extreme limits (or minimum requirements) for some organisms on Earth.
"Evidence has built over the past 20 years that there's an incredible amount of biomass in the Earth's subsurface, in the crust and marine sediments, perhaps as much as all the plants and animals on the surface," microbiologist James Holden at the University of Massachusetts said in a statement. "We're interested in the microbes in the deep rock, and the best place to study them is at hydrothermal vents at undersea volcanoes. Warm water flows bring the nutrient and energy sources they need."
One way to figure out what's hidden beneath Earth's crust in extreme environments is to figure out the energy requirements of an organism and then see if various spots meet these thresholds for life. "We're really interested in the equivalent of, 'What is the size of your paycheck and what's the cost of living?'" Holden told LiveScience. "How much energy is available for microorganisms: the paycheck. And what's the lower threshold – they need this much energy to live in this environment." [Gallery: Unique Life at Deep-Sea Vents]
To do this, the researchers collected methanogens from hydrothermal vents and tried growing them (along with commercially bought microbes) on different levels of hydrogen. From these experiments, they found the bare minimum of hydrogen that these microbes needed to survive (they all needed about the same concentrations).
Next, Holden and colleagues sent the deep submersible vehicle Alvin to test out the findings at two spots: the Axial volcano and the Endeavor segment, both observatory sites along an undersea mountain range well off the coast of Washington state and Oregon and about 1 to 1.5 miles (1.6 to 2.4 kilometers) below the surface of the Pacific Ocean.
Alvin collected samples from the sites' black smokers, where mineral-rich, superheated water ? up to 662 degrees Fahrenheit (350 degrees Celsius) ? spews out of Earth's crust through cracks in the seafloor, and it also took samples from surrounding, lower-temperature waters.
The hydrogen limits found in the lab held up in the field. At the Axial volcano site, where the scientists found hydrogen levels above the lab-determined threshold, they also found evidence of methanogenic microbes; at Endeavour, hydrogen levels were below the threshold, with evidence of methane-producers largely absent. However, they found heat-loving methanogens could survive by feeding on hydrogen produced by other extreme organisms living near the vent.
In addition to painting a more comprehensive picture of Earth's biodiversity today, the findings may reveal what life was like on early Earth, "where we think [life] was independent of sun and oxygen," Holden said.
His research also can be used beyond Earth, he says; the astrobiology community uses this sort of data to rule in or out the possibility of past extraterrestrial life on, say, Mars or the Jupiter moon Europa.
"How much energy is available and what's the 'cost of living' for these organisms, and could Mars have had enough energy to support this kind of life?" Holden said during a telephone interview.
The research, detailed this week in the journal Proceedings of the National Academy of Sciences, was supported by the National Science Foundation, NASA Astrobiology Institute and the National Oceanographic and Atmospheric Administration.
Follow LiveScience on Twitter @livescience. We're also on Facebook & Google+.
Copyright 2012 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Our 2024 Coverage Needs You
It's Another Trump-Biden Showdown — And We Need Your Help
The Future Of Democracy Is At Stake
Our 2024 Coverage Needs You
Your Loyalty Means The World To Us
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
The 2024 election is heating up, and women's rights, health care, voting rights, and the very future of democracy are all at stake. Donald Trump will face Joe Biden in the most consequential vote of our time. And HuffPost will be there, covering every twist and turn. America's future hangs in the balance. Would you consider contributing to support our journalism and keep it free for all during this critical season?
HuffPost believes news should be accessible to everyone, regardless of their ability to pay for it. We rely on readers like you to help fund our work. Any contribution you can make — even as little as $2 — goes directly toward supporting the impactful journalism that we will continue to produce this year. Thank you for being part of our story.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
It's official: Donald Trump will face Joe Biden this fall in the presidential election. As we face the most consequential presidential election of our time, HuffPost is committed to bringing you up-to-date, accurate news about the 2024 race. While other outlets have retreated behind paywalls, you can trust our news will stay free.
But we can't do it without your help. Reader funding is one of the key ways we support our newsroom. Would you consider making a donation to help fund our news during this critical time? Your contributions are vital to supporting a free press.
Contribute as little as $2 to keep our journalism free and accessible to all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. Would you consider becoming a regular HuffPost contributor?
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. If circumstances have changed since you last contributed, we hope you'll consider contributing to HuffPost once more.
Support HuffPostAlready contributed? Log in to hide these messages.