Image: Mars meteorite
The Mars meteorite ALH84001 shown here has been a source of controversy since its discovery in 1984.
updated 10/4/2011 5:38:21 PM ET 2011-10-04T21:38:21

Ancient Mars was warm enough to support liquid water in at least one site on its surface, according to clues from a 4.1-billion-year-old meteorite from Mars, scientists say.

Still, how long and widespread such warmth was remains highly uncertain, meaning it is still a mystery as to whether Mars could have once supported life, researchers added.

Numerous missions to Mars have revealed a host of features on the Red Planet that suggest it was once warm enough for liquid water to run across its surface, including what appear to be valley networks, river deltas and minerals that required water to form. However, current models of early Mars' climate still cannot explain how such mild temperatures could have existed, as the sun was much weaker back then, leading some to ask whether these features might have been created by winds or other mechanisms. [ Photos: The Search for Water on Mars ]

Now analysis of an ancient meteorite from Mars — the oldest known fragment of the Red Planet's crust astronomers have — has revealed "the first direct evidence for relatively warm temperatures on the surface of early Mars," study lead author Itay Halevy, a geochemist at the California Institute of Technology, told

Famous Mars meteorite
The Mars rock in question is known as the Martian meteorite ALH84001. It was discovered in Antarctica in 1984.

The meteorite was likely blasted off Mars by a cosmic impact, eventually landing on Earth. The rock is the same meteorite from Mars at the center of a long-running debate over whether its strange features are the result of microbial fossils or just regular geochemistry.

By testing a sample from this 5-pound (2-kilogram) meteorite, Halevy and his colleagues inferred the watery nature and mild temperature of the environment the rock originally formed in on early Mars.

Specifically, the researchers analyzed isotopes of carbon and oxygen in carbonates in the meteorite. All isotopes of an element have the same number of protons in their atoms, but each has a different number of neutrons — for instance, atoms of carbon-12 each have six neutrons while atoms of carbon-13 each have seven.

How the experiment works
Relatively heavy isotopes such as carbon-13 and oxygen-18 prefer to bond with each other rather than lighter isotopes of their element. This tendency depends on temperature — the cooler it is, the more likely they are to bond. As such, by measuring levels of these two isotopes in the carbonates, the researchers could determine what temperature the rock formed at, Halevy said. [ 5 Bold Claims of Alien Life ]

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The researchers dissolved 3 grams of the carbonates in the sample in acid, which released carbon dioxide, which possesses both carbon and oxygen. By comparing the carbon-13 and oxygen-18 levels in this carbon dioxide, they estimate the carbonates formed at about 64 degrees Fahrenheit (18 degrees Celsius).

The carbonates also apparently formed in a watery environment, one that gradually dried out, Halevy said. The scientists reached this conclusion after their analysis found the solution in which this material grew from apparently lost its lighter carbon and oxygen isotopes over time.

The lighter isotopes of carbon and oxygen prefer to make their way into gases such as water vapor while heavier isotopes favor denser homes such as liquid water. The loss of these lighter isotopes is consistent with the loss of water vapor and carbon dioxide gas from a watery reservoir, Halevy and his colleagues suggested.

However, although these findings suggest that parts of Mars were warm and watery, "they do not mean there was life on Mars," Halevy cautioned.

"We found one environment there was water and mild temperatures, but we don't know how long it was warm and if it was warm elsewhere, so this alone cannot reflect on how suitable Mars was for hosting life." He added more data from upcoming missions such as the Mars Science Laboratorycould help better understand the history of the Red Planet.

Halevy and his colleagues Woodward Fischer and John Eiler detailed their findings online Oct. 3 in the Proceedings of the National Academy of Sciences.

Follow contributor Charles Q. Choi on Twitter @cqchoi. Visit for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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