The atmosphere of Mars may not have escaped into space billions of years ago, scientists say. Instead, the bulk of Mars' carbon dioxide gas could be locked inside Martian rocks.

Most of Mars' carbon dioxide vanished about 4 billion years ago, leaving a cold planet covered in a thin veneer of gas. But a new analysis of a Martian meteorite claims that some of the carbon dioxide disappeared into Mars itself, and not out into space as previous studies have suggested.

"This is the first direct evidence of how carbon dioxide is removed, trapped and stored on Mars," said Tim Tomkinson, lead study author and a geochemist at the University of Glasgow in the United Kingdom. "We can find out amazing things about Mars from the very small amount of sample that we have." [7 Biggest Mysteries of Mars]

Tomkinson and his colleagues probed the history of the Mars atmosphere by analyzing minerals in a tiny slice of the Lafayette meteorite, a Mars rock blasted toward Earth 11 million years ago. The Lafayette is one of several Martian meteorites called the Nakhlites, thought to have been ejected out of a vast volcanic plateau by a comet impact.

mars atmosphereFalse color image of a slice of the Lafayette meteorite with overlaid X-ray maps of silicon (green), iron (red) and calcium (blue). Carbonate (orange) replaced olivine (blue); both surrounded by veins of clay (green).

The meteorites are 1.3-billion-year-old basalt, a volcanic rock rich in the mineral olivine. Long before their space journey, water altered the rock, leaving behind microscopic fractures filled with clays and carbonates. Radiometric dating indicates these minerals formed some 625 million years ago. The research is detailed in the Oct. 22 edition of the journal Nature Communications.

Tomkinson's team discovered that Lafayette's siderite, an iron-rich carbonate mineral, formed through carbonation. (This is the same process proposed for carbon sequestration on Earth.) When water and carbon dioxide gas combine with olivine minerals in the basalt, the ensuing chemical reaction creates carbonate and silicate minerals, trapping the gas.

The results mean liquid water flowed on Mars within the last 700 million years, either from geothermal or hydrothermal heating, Tomkinson said. "This process could have been an even bigger player when Mars was thought to be a warmer and wetter planet," he added. "This process was still occurring when conditions were unfavorable for carbonation. It could potentially have been a much bigger mechanism when Mars had a thicker atmosphere 4 billion years ago," Tomkinson told

NASA's Mars spacecraft and rovers have already found widespread carbonate deposits on the planet. And NASA's next Mars spacecraft will help probe the fate of the planet's atmosphere.

The space agency's MAVEN mission, short for Mars Atmosphere and Volatile EvolutioN, will test whether the volatile gases were ripped away into space or trapped on the surface in ice and rocks. One popular model suggests the atmosphere was lost to space when Mars lost its magnetic field. MAVEN's launch window opens Nov. 18.

Email Becky Oskin or follow her @beckyoskin. Follow us @Spacedotcom, Facebook or Google+. Originally published on

Copyright 2013, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Also on HuffPost:

  • Shallow Irregular Pits with Raised Rims

    Researchers are still trying to figure out what caused these "mystery" features. One intriguing theory suggests they were sculpted by ancient glaciation.

  • Dune Fields and Wall Rock in Coprates Chasma

    Researchers think that the dune sand, wall spurs and boulders shown here are all partially composed of olivine, a mineral that is highly susceptible to weathering by aqueous (water) processes.

  • Sedimentary Bedrock Diversity in Terby Crater

    From the HiRISE website: "Terby Crater, sitting on the northern rim of Hellas Basin, has been filled by sedimentary deposits, perhaps deposited by or in water."

  • Raindrops of Sand in Copernicus Crater

    The dark features here look like raindrops, but are actually sand dunes. This spot was targeted an infrared spectrometer on the Mars Orbiter because the dunes are rich in the mineral olivine. Olivine-rich dunes are very rare on Earth, as olivine rapidly weathers to clays in a wet environment. There is also olivine-rich bedrock in the central peaks of Copernicus Crater on the Moon. (Caption: Alfred McEwen)

  • Bright Tracks from Bouncing and Rolling Boulders

    This image shows a well-preserved impact crater. A closeup view highlights distinctive bright lines and spots on the steep slope on the north side. No such pattern was visible when HiRISE imaged this crater 5 years ago (2.6 Martian years ago), in March 2008. The discontinuous bright spots indicate bouncing, thus these features are interpreted to be a result of boulders bouncing and rolling down the slope. Where did the boulders come from? Maybe they fell from the crater's steep upper cliffs, although we don't see any new bright features there that point to the source. Maybe the rocks were ejected from a new impact event somewhere nearby. Why are the trails bright? Perhaps the shallow subsurface soil here is generally brighter than the surface soil, as revealed by the Spirit rover in a part of Gusev Crater. It can't be bright from ice because this is a warm equator-facing slope seen in the summer. (Caption: Alfred McEwen)

  • Ridges and Grooves That Wave and Buckle on a Valley Floor

    Long linear ridges and grooves curve, wave, and buckle across most of this image. Here, as elsewhere on Mars, these linear ridges and grooves fill a valley floor, hence their name, "lineated valley fill." Because these features are only found in valleys in the middle latitudes (30 to 60 degrees) of the Northern and Southern hemispheres, scientists had long suspected that they were associated with some ancient climate that had prevailed in that latitudinal band. Based on peering beneath the surface using radar, scientists now think that lineated valley fill is probably merely a rocky veneer atop a glacier of nearly pure ice! The rocks that make up the linear ridges and grooves were oriented by the ancient flow of the glacier underneath. (Caption: Ethan Schaefer)

  • Megabreccia on the Floor of an Impact Crater

    "'Megabreccia' is a term we use to describe jumbled, fragmented blocks of rock larger than 1 meter across, in a matrix of finer-grained materials," per the HiRISE website. "It's the result of energetic processes, typically from an impact event."

  • Defrosting of Dunes with Large Gullies

    The purpose of this observation is to image dunes where substantial "gullies" formed in the previous Martian winter. These features likely formed due to carbon dioxide defrosting or weight that caused the surface to slump. The gullies at this site are particularly large, which is intriguing, suggesting that this site be monitored to see if stages of gully formation or details of activity can be observed. (Caption: HiRISE Science Team)

  • Martian Honeycomb Hideout

    The most striking aspect of this image is the honeycomb-like pattern of the dunes. This is a seasonal monitoring site, meaning HiRISE takes pictures across the seasons to view what changes occur and what causes them. The surface here is covered with seasonal carbon dioxide frost. In this case, we can compare locations of cracks in the frost to previous images. (Caption: HiRISE Science Team)