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Building blocks of life found in famous Mars meteorite

A rock fragment of Martian meteorite ALH84001 (left). An enlarged area (right) shows the orange-colored carbonate grains on the host orthopyroxene rock.
A rock fragment of Martian meteorite ALH84001 (left). An enlarged area (right) shows the orange-colored carbonate grains on the host orthopyroxene rock.
(Image: © Koike et al. (2020) Nature Communications)

Ancient Mars is looking better and better as an abode for life.

The famed Mars meteorite Allan Hills 84001 (ALH84001) contains 4-billion-year-old native organic molecules, the carbon-containing building blocks of life as we know it, a new study suggests. 

And that's not all. The organics contain nitrogen, another ingredient that Earth life depends on, and were found within carbonate minerals, which usually form in groundwater. So the discovery adds to an emerging picture of a wet and potentially habitable Mars in the distant past, study team members said. 

Related: Mars life: Exploration and evidence

This picture has been fleshed out by a range of observations over the years, including recent work by NASA's Mars rover Curiosity. Curiosity has spotted ancient native organics as well, and the car-size robot found evidence of a long-ago, but long-lived, lake-and-stream system at its study site, the Red Planet's 96-mile-wide (154 kilometers) Gale Crater. (Mars is very different today, of course; the planet transitioned to a cold and dry world about 3.5 billion years ago, after it lost most of its atmosphere to space.) 

Scientists think ALH84001 was blasted off Mars by a powerful impact 16 million years ago and came down to Earth much later, about 13,000 years ago. 

The meteorite, which was discovered in Antarctica in 1984, has been in the spotlight before. In 1996, a research team led by David McKay of NASA's Johnson Space Center claimed to have found compelling evidence of ancient microbial Mars life in ALH84001. The scientists cited four main lines of evidence, one of which involved carbonate globules and organic molecules.

The scientific community has generally deemed this collection of evidence to be unconvincing, stressing that abiotic factors could explain the observations. But the study authors stand by their original conclusions, and debate over ALH84001 continues to this day.

In the new study, researchers led by Mizuho Koike, of the Institute of Space and Astronautical Science at the Japan Aerospace Exploration Agency, looked at the Mars rock in a new way. The team used novel and highly precise analytical techniques, including a type of X-ray spectroscopy, to detect nitrogen in ALH84001 and trace it to the carbonate minerals. 

This was a first; nobody had found nitrogen-containing organics in the rock before, team members said. The researchers think the organics were trapped in the carbonate about 4 billion years ago; they said their techniques minimized the chance of terrestrial contamination, which is always a concern with Mars meteorites. 

To be clear: The organics are not evidence of Mars life; such compounds can be produced abiotically as well as biotically. And there are other important questions about the ALH84001 organics as well, such as where they formed. 

"There are two main possibilities: either they came from outside Mars, or they formed on Mars," study co-author Atsuko Kobayashi, of the Earth-Life Science Institute at the Tokyo Institute of Technology, said in a statement

"Early in the solar system's history, Mars was likely showered with significant amounts of organic matter, for example from carbon-rich meteorites, comets and dust particles," Kobayashi added. "Some of them may have dissolved in the [Martian] brine and been trapped inside the carbonates."

Scientists have a chance to make some real progress on the Mars-life question soon. NASA's Mars 2020 rover Perseverance, which is scheduled to launch in July, will hunt for signs of ancient Red Planet organisms and collect samples for future return to Earth. Once this pristine Mars material lands here — which could happen as soon as 2031 — researchers around the world will be able to scrutinize it in great detail.

The new study was published online April 24 in the journal Nature Communications.

Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook

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  • rod
    This report was interesting. ALH84001 in the news off and on since mid-1990s. Remember, Mars atmosphere has molecular nitrogen too, however small compared to CO2 abundance. Nitrogen at Mars has been known for a long while now.
    Reply
  • Torbjorn Larsson
    Yes, it is interesting! Not least because ALH84001 was buried close to the subsurface for a very long time and so points to early organics survival that Perseverance may find. The nitrogen chemistry points to a more pH neutral environment at the time, which is also promising.
    Reply
  • rod
    Yes, searches for life on Mars is ongoing with some notable consensus science views from 1907 and 1943 that considered vegetation grew on Mars documented here.

    “If vegetation exists on Mars, as Prof. Lowell would have us believe, the existence of a flora is ground for suspecting a fauna. On Mars we find ourselves confronted in the canals and oases by precisely the appearance which the planet should show if it is an inhabited world. Dearth of water is the key to the character of the canals. The only available water on Mars is that coming from the semi-annual melting at the one or the other cap of snow. If there are intelligent beings on Mars, they must find some means of conducting the scant supply of water from the poles to the centers of populations.” —Scientific American, July 1907 More gems from Scientific American’s first 175 years can be found on our shiny anniversary page."

    “If, as appears to be probable, vegetation exists on Mars, life has developed on two out of the three planets in our system where it has any chance to do so. With this as a guide, it appears now to be probable that the whole number of inhabited worlds within the Galaxy is considerable. To think of thousands, or even more, now appears far more reasonable than to suppose that our planet alone is the abode of life and reason. What the forms of life might be on these many worlds is a question before which even the most speculative mind may quail. Imagination, in the absence of more knowledge of the nature of life than we now possess, is unequal to the task. There is no reason, however, against supposing that, under favorable conditions, organisms may have evolved which equal or surpass man in reason and knowledge of Nature. And, let us hope, in harmony among themselves!” —Scientific American, July 1943

    There is at least 200 Martian meteorites in the current inventory. ALH84001 was the most hopeful to contain fossils of life on Mars reported during the Clinton Administration. Future searches for life on Mars present or Mars past, could return null results like all past efforts since 1907 through ALH84001 and some other Martian meteorites. The Galilean moons are confirmed as orbiting Jupiter by Galileo and still observed with backyard telescopes today. However, confirmation of life on Mars today or in the past, remains to be demonstrated.
    Reply
  • Catastrophe
    Come on Rod - Lowell is long gone.
    Where are you taking this thread?

    I have the utmost respect for your intelligence but, come on, does it need to be that circuitous? Just a little more succinct would be appreciated . . . . . . . . . or am I alone in this?
    Reply
  • YetAnotherBob
    Catastrophe said:
    Come on Rod - Lowell is long gone.
    Yes. Lowell was wrong on several fronts. But the point is, I think that there is a long string of scientists that believed or hoped that there would be life on Mars. Now we are down to just hoping for bacteria, but that hope is still there. It goes back to long before Lowell too.

    Personally, given the political climate of today, I hope we don't find life. It will make the current plans of people like Robert Zubrin and Elon Musk so much easier.

    Hopefully there will be life on Mars in 20 years. Human life.
    Reply
  • rod
    *a long string of scientists that believed or hoped that there would be life on Mars* FYI. This is exactly why I presented the short recap from 1907 through ALH84001 today illustrating this was belief and not science fact. The *believed* or *hoped* does not follow the same standard of observation and verification that Galileo used against the geocentric solar system teachers. Perhaps someday, science will show life existed on Mars or still does, however, at present this is not confirmed by the scientific method like the Galilean moons, thus it remains a belief or hope.
    Reply
  • Catastrophe
    Depends on what you mean by building blocks.
    Bit of C bit of H bit of N bit of O
    Proves NOCH

    Suggests so-called building blocks present.
    Still needs a builder and some mortar.
    Reply
  • Torbjorn Larsson
    Catastrophe said:
    Depends on what you mean by building blocks.
    Bit of C bit of H bit of N bit of O
    Proves NOCH

    Suggests so-called building blocks present.

    Yes, building blocks of biomolecules that on Earth evolved and are evolving still. The current identified pathway was through alkaline hydrothermal vents, that we know Mars have had (Spirit got stuck and died in the silica produced by one, say).

    The short time until life evolved on Earth means early evolution was also easy in these conditions, so should happen where we find them. Early Mars would have been a good place (and so is late Enceladus too, plumes driven by the same type of vents).

    But if we don't find extant or extinct life, we have to reassess. Likely Mars has life within the crust even today, though spotty such (inhomogeneous crust, one part of which is volatile rich). That should not mix with Earth life or vice versa, it is the current geosphere specialist so Earth prokaryotes - who will be mostly coevolved with us or our plants - should have a hard time to get to resources.
    Reply
  • Cosmo47
    I am reminded of a Star Trek Next Generation episode where miners were working on a 'lifeless' planet but suffered malfunctions in their technology. We found out it was caused by 'life' whose home on the planet was a few feet beneath the surface in a layer of salinity that existed across much of the planet. "Who would have thought that was possible?" exclaimed the miners.

    On Mars I 'hope/believe/expect' to find microbial life in layer(s) of brine or saline waters also just below the surface where such liquid exists. My second choice for finding life on Mars is in its caves, where I expect that some of the water from its rivers and lakes and oceans disappeared to instead of vaporizing into space.

    But all of this is just speculation, of course. I would never speak as if it were fact. I will leave it to the rovers and if not them, then to the future humans on Mars to prove me right or wrong. But a man can dream, after all.
    Reply
  • rod
    "But all of this is just speculation, of course. I would never speak as if it were fact."

    FYI, an important statement and observation here I feel. The meteorite Allan Hills 84001 in this report has a long history of reworked radiometric dating using different isotopes to identify the object's *true age*. Early ages were 4.63E+9 years old, and others 4.5 billion years old or older. More recent dating accepted for ALH84001 was 4.09E+9 years old. The 4.09E+9 age fits better with the *Noachian* period interpreted for Mars past and when life could be there. All Martian meteorites, wikipedia reports 99, other reports I have claim 200 Martian meteorites, have various radiometric ages reported along with different CRE ages too.
    Reply