The mystery of how Mars meteorites reach Earth may finally be solved

a black rock
A fragment of a Martian meteorite that was found in the Allan Hills in Antarctica on December 27, 1984, by a team of American meteorite hunters. (Image credit: NASA)

Scientists have discovered that the force needed to eject rocks from the surface of Mars that eventually pelt Earth as meteorites is actually much lower than previously believed. 

Meteorites from a variety of sources have been discovered across Earth's surface for thousands of years, but Mars wasn't suggested as a possible source of this bombardment until the 1970s when measurements of the Martian atmosphere made by NASA's Viking orbiters were found to match gases locked in these space rocks. Nonetheless, it remained unknown how exactly these rocks might have made it all the way from the Red Planet to Earth.

In a new study, scientists from the California Institute of Technology (Caltech) and the Jet Propulsion Laboratory (JPL), simulated the "shock pressure" that is experienced by Mars rocks as they are ejected from the planet. In doing so, researchers found it may not be as difficult to catapult a rock from Mars to space as was previously believed.

Related: Building blocks of life found in famous Mars meteorite

"We're not on Mars, so we can't watch a meteorite strike in person," team member and JPL planetary scientist Yang Liu said in a statement. "But we can recreate a similar kind of impact in a lab setting. By doing so, we found it takes much less pressure to launch a Mars meteorite than we thought."

To make it from the surface of Mars, through the Martian atmosphere, in and out of the near-vacuum of space and then through Earth's atmosphere and onto the surface of our planet, the rocks must survive massive temperatures and pressures and an eventual crash landing.

Until engineers can figure out a way to collect and return Martian samples, these meteorites are the only way they can study the Red Planet's rocks up close and personal. While the meteorites are being studied, other researchers are working to better understand the nature of the impacts upon Mars that could launch pieces of the Red Planet in the first place.

And as it turns out, Martian meteorites contain other details locked within them about their journey from the Red Planet to Earth. 

A meteorite that originated on Mars in a display case in Maine Mineral and Gem Museum. (Image credit: Ben McCanna/Portland Press Herald via Getty Images)

The glassy material maskelynite is created when the mineral plagioclase is exposed to extreme pressure like those caused by giant impacts. That means finding maskelynite within the rock can hint at the kind of pressures they have been exposed to. Over the last five years, Martian meteorites have been found with a mix of plagioclase and maskelynite which puts constraints on the amount of pressure they must have experienced. 

The Caltech/JPL team set about smashing plagioclase-containing rocks from Earth to observe how high pressures cause the mineral to transform. This involved using a powerful gun to blast the rocks with projectiles fired at five times the speed of sound, simulating the kinds of pressures rocks ejected from Mars would experience. 

Previous experiments showed plagioclase becomes maskelynite at a shock pressure of 30 gigapascals (GPa), which is 300,000 times the atmospheric pressure on Earth at sea level. These past tests have required reverberating shock waves through a steel chamber, something that doesn't give an accurate picture of what happens during impacts on Mars, however. 

In these new experiments, without that steel chamber acting on the shock waves, the scientists found that the transition between plagioclase becomes maskelynite actually occurred at just 20 GPa.

"It has been a significant challenge to model an impact that can launch intact rocks from Mars while shocking them to 30 GPa," Caltech Eleanor and John R. McMillan Professor of Geology and Geochemistry Paul Asimow said in a separate statement. "In this context, the difference between 30 GPa and 20 GPa is significant."

Designated Northwest Africa (NWA) 7034, and nicknamed "Black Beauty," this Martian meteorite weighs approximately 11 ounces (320 grams). (Image credit: NASA)

The results are in line with observations of other high-pressure minerals in meteorites that support the idea Martian meteorites experience shock pressures of less than 30 GPa on ejection from the Red Planet. 

Armed with these new shock pressure parameters, scientists may eventually be able to trace Martian meteorites to the giant impacts that initially sent them hurtling through space. 

"The more accurately we can characterize the shock pressures experienced by a meteorite, the more likely it becomes that we can identify the impact crater on Mars from which it originated," Asimow concluded.

The team's research was published in the journal Science Advances. 

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Robert Lea
Contributing Writer

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

  • rod
    My observations. Mars escape velocity is a bit more than 5 km/s so blasting off pieces into space is plausible from large impacts. Dating the time and place of these large impacts looks difficult. Consider the Martian meteorite, NorthWest Africa 7533.

    Ref - Regolith breccia Northwest Africa 7533: Mineralogy and petrology with implications for early Mars,, January 2017. The abstract shows several different radiometric ages that must be reconciled, 4.43 Gyr to 1.35-1.4 Gyr for some ages. The cosmic ray exposure age is about 5 Myr. “The Martian origin of the pyrite is demonstrated by its fracturing caused by shock (Lorand et al. 2015), possibly during the launch event. Wittmann et al. (2015) using Fe and Th abundances, and the ~5 Ma exposure age of Cartwright et al. (2014), suggest one possible launch site for the breccias, the young rayed crater Gratteri. This crater has also been suggested as the source of ALH 84001 (Tornabene et al. 2006).”, ref - Regolith breccia Northwest Africa 7533: Mineralogy and petrology with implications for early Mars,, 25-October-2016. “Abstract Northwest Africa 7533, a polymict Martian breccia, consists of fine-grained clast-laden melt particles and microcrystalline matrix. While both melt and matrix contain medium-grained noritic-monzonitic material and crystal clasts, the matrix also contains lithic clasts with zoned pigeonite and augite plus two feldspars, microbasaltic clasts, vitrophyric and microcrystalline spherules, and shards…”

    The cosmic ray exposure ages for the Martian meteorites should be shown along with various radiometric ages obtained. Likely will show large impacts ejecting pieces of Mars in the recent past, so catastrophism on Mars still operating perhaps.
  • billslugg
    From the abstract:
    50Mya - the meteoroid ejected into space from Mars
    1.4Gya - it was a rock on Mars, pertially melted
    4.6 Gya - completely melted
  • rod
    billslugg said:
    From the abstract:
    50Mya - the meteoroid ejected into space from Mars
    1.4Gya - it was a rock on Mars, pertially melted
    4.6 Gya - completely melted
    The article cites a more recent report,, 'Shock-recovered maskelynite indicates low-pressure ejection of shergottites from Mars', 03-May-2023. I did not find specific radiometric ages or exposure ages provided or any specific ejection times from Mars. The paper does briefly mention this, "In turn, a decrease in the estimate of shock pressure in the shergottites increases the rarity of ejection of unmelted rocks and increases the probability that the known shergottites were ejected by fewer impact events, given their narrow range of cosmic ray exposure ages (51)." The ref - 51R.
    The NorthWest Africa 7533 shows an exposure age of 5 Myr, not a 50 Myr ejected into space from Mars, ref -
    It seems very difficult to sort all of the different radiometric ages found (reported values) and the exposure ages (reported) for all the Martian meteorites. I note this from the paper about NorthWest Africa 7533. "(2) The lithification age is ~1.4 Ga. Yin et al. (2014) argued that some of the zircon analyses at the lower intercept were actually concordant grains that crystallized from melts at ~1.4 Ga. This led them to interpret the lithification age of the breccia as ~1.4 Ga. This model of the assembly time cannot explain the absence of zircons between 4.35–1.4 Ga, but is more permissive to sampling a very wide range of Martian history (~3 Ga), even if not recorded by zircon-forming events. Resolving these two models is essential to fully reading the record of ancient Mars from this breccia."

    I find the various dating methods and reconciliation explanations - intriguing. :)
  • rod
    FYI, the article using ref 51 I found at the NASA ADS Abstract site.

    Noble gases in 18 Martian meteorites and angrite Northwest Africa 7812—Exposure ages, trapped gases, and a re-evaluation of the evidence for solar cosmic ray-produced neon in shergottites and other achondrites,, Feb-2016.

    "We present noble gas data for 16 shergottites, 2 nakhlites (NWA 5790, NWA 10153), and 1 angrite (NWA 7812). Noble gas exposure ages of the shergottites fall in the 1-6 Ma range found in previous studies. Three depleted olivine-phyric shergottites (Tissint, NWA 6162, NWA 7635) have exposure ages of ~1 Ma, in agreement with published data for similar specimens. The exposure age of NWA 10153 (~12.2 Ma) falls in the range of 9-13 Ma reported for other nakhlites. Our preferred age of ~7.3 Ma for NWA 5790 is lower than this range, and it is possible that NWA 5790 represents a distinct ejection event."

    Exposure ages shown are very young.
  • Atilla De Bum
    That large canyon on Mars appears to be gouged out from a glancing blow from a large asteroid. An impact of that size could have easily stripped the atmosphere from the planet and thrown untold tons of surface material into space.