Scientist uncovers red planet's climate history in unique meteorite

Aug 27, 2014
Mars. Image: NASA

Was Mars—now a cold, dry place—once a warm, wet planet that sustained life? And if so, how long has it been cold and dry?

Research underway at the National High Magnetic Field Laboratory may one day answer those questions—and perhaps even help pave the way for future colonization of the Red Planet. By analyzing the chemical clues locked inside an ancient Martian meteorite known as Black Beauty, Florida State University Professor Munir Humayun and an international research team are revealing the story of Mars' ancient, and sometimes startling, climate history.

The team's most recent finding of a dramatic climate change appeared in Nature Geoscience, in the paper "Record of the ancient Martian hydrosphere and atmosphere preserved in zircon from a Martian meteorite."

The scientists found evidence for the climate shift in minerals called zircons embedded inside the dark, glossy meteorite. Zircons, which are also abundant in the Earth's crust, form when lava cools. Among their intriguing properties, Humayun says, is that "they stick around forever."

"When you find a zircon, it's like finding a watch," Humayun said. "A zircon begins keeping track of time from the moment it's born."

Last year, Humayun's team correctly determined that the zircons in its Black Beauty sample were an astonishing 4.4 billion years old. That means, Humayun says, it formed during the Red Planet's infancy and during a time when the planet might have been able to sustain life.

"First we learned that, about 4.5 billion years ago, water was more abundant on Mars, and now we've learned that something dramatically changed that," said Humayun, a professor of geochemistry. "Now we can conclude that the conditions that we see today on Mars, this dry Martian desert, must have persisted for at least the past 1.7 billion years. We know now that Mars has been dry for a very long time."

The secret to Mars' climate lies in the fact that zircons (ZrSiO4) contain oxygen, an element with three isotopes. Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons—sort of like members of a family who share the same last name but have different first names.

On Mars, oxygen is distributed in the atmosphere (as carbon dioxide, molecular oxygen and ozone), in the hydrosphere (as water) and in rocks. In the thin, dry Martian atmosphere, the sun's ultraviolet light causes unique shifts in the proportions in which the three isotopes of oxygen occur in the different atmospheric gases.

So when water vapor that has cycled through the Martian atmosphere condenses into the Martian soil, it can interact with and exchange oxygen isotopes with zircons in the soil, effectively writing a climate record into the rocks. A warm, wet Mars requires a dense atmosphere that filters out the ultraviolet light making the unique isotope shifts disappear.

In order to measure the proportions of the oxygen isotopes in the zircons, the team, led by scientist Alexander Nemchin, used a device called an ion microprobe. The instrument is in the NordSIMS facility at the Swedish Museum of Natural History, directed by team member Martin Whitehouse.

Because of these precise measurements, said Humayun, "we now have an isotopic record of how the atmosphere changed, with dates on it."

The Black Beauty meteorite Humayun's team is studying was discovered in the Sahara Desert in 2011. It's also known as NWA 7533, which stands for Northwest Africa, the location where it was found.

In all, more than five pieces of Black Beauty were found by Bedouin tribesmen, who make a living scouring the Sahara for meteorites and fossils that they can sell. The zircons analyzed by Humayun's team were from Black Beauty samples kept in Paris.

Explore further: SpaceX mile-high escape test will feature 'Buster' the dummy

Related Stories

Meteorites yield clues to Martian early atmosphere

Apr 16, 2014

(Phys.org) —Geologists who analyzed 40 meteorites that fell to Earth from Mars unlocked secrets of the Martian atmosphere hidden in the chemical signatures of these ancient rocks. Their study, published ...

Martian rock from Sahara desert unlike others

Jan 03, 2013

Scientists are abuzz about a coal-colored rock from Mars that landed in the Sahara desert: A yearlong analysis revealed it's quite different from other Martian meteorites. Not only is it older than most, ...

Meteorites' age is at center of Mars history debate

Aug 13, 2013

Planetary scientists dream of sending a geologist to Mars to study its rocks by hand. Until then, they have to settle for examining meteorites - chunks of the Red Planet that land on Earth after hurtling through ...

Moroccan desert meteorite delivers Martian secrets

Oct 11, 2012

(Phys.org)—A meteorite that landed in the Moroccan desert 14 months ago is providing more information about Mars, the planet where it originated. University of Alberta researcher Chris Herd helped in the ...

Recommended for you

Video: An enormous "plasma snake" erupts from the Sun

May 01, 2015

Over the course of April 28–29 a gigantic filament, briefly suspended above the surface of the sun, broke off and created an enormous snakelike eruption of plasma that extended millions of miles out into ...

20 ExoWorlds are now available for naming proposals

May 01, 2015

Although people have been naming celestial objects for millennia, the IAU has the task of assigning scientifically recognised names to newly discovered celestial bodies by its member countries. The NameExoWorlds ...

Giant telescope takes close look at Jupiter's moon Io

May 01, 2015

With the first detailed observations through imaging interferometry of a lava lake on a moon of Jupiter, the Large Binocular Telescope Observatory places itself as the forerunner of the next generation of ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.