Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mars: Red Planet's Rapid Formation Explains Its Small Size Relative to Earth

26.05.2011
Mars developed far more quickly than our blue planet

Mars developed in as little as two to four million years after the birth of the solar system, far more quickly than Earth, according to results of a new study published in this week's issue of the journal Nature.


Mars is planetary embryo that never collided with other embryos to form an Earthlike planet.

The red planet's rapid formation helps explain why it is so small, say the study's co-authors, Nicolas Dauphas at the University of Chicago and Ali Pourmand at the University of Miami.

Their research was funded by the National Science Foundation (NSF).

Mars probably is not a terrestrial planet like Earth, which grew to its full size over 50 to 100 million years via collisions with other small bodies in the solar system, said Dauphas, a geophysicist.

"Earth was made of embryos like Mars, but Mars is a stranded planetary embryo that never collided with other embryos to form an Earthlike planet," Dauphas said.

The new work provides evidence for this idea, which was first proposed 20 years ago on the basis of planetary growth simulations.

It likely will change the way planetary scientists view Mars, said Pourmand, a marine geologist and geophysicist. "We thought that there were no embryos in the solar system to study, but when we study Mars, we are studying embryos that eventually made planets like Earth."

There had been large uncertainties in the formation history of Mars because of the unknown composition of its mantle, the rock layer that underlies the crust.

"Now we can shrink those uncertainties to the point where we can do interesting science," Dauphas said.

Dauphas and Pourmand were able to refine the age of Mars by using the radioactive decay of hafnium to tungsten in meteorites.

Hafnium 182 decays into tungsten 182 in a half-life of nine million years. This relatively rapid decay means that almost all hafnium 182 will disappear in 50 million years, providing a way to assemble a fine-scale chronology of early events in the solar system.

"To apply that system you need two gradients," Pourmand explained. "You need the hafnium-tungsten ratio of the mantle of Mars and you need the tungsten isotopic composition of the mantle of Mars."

The latter was well known from analyses of martian meteorites, but not the former.

Previous estimates of the formation of Mars ranged as high as 15 million years because the chemical composition of the martian mantle was largely unknown.

Scientists still wrestle with large uncertainties in the composition of Earth's mantle because of processes such as melting.

"We have the same problem for Mars," Dauphas said.

Analyses of martian meteorites provide clues about the mantle composition of Mars, but their compositions also have changed.

Solving some lingering unknowns about the composition of chondrites, a common type of meteorites, provided the data needed.

As essentially unaltered debris left over from the birth of the solar system, chondrites serve as a Rosetta stone for deducing planetary chemical composition.

Cosmochemists have intensively studied chondrites, but still poorly understand the abundances of two categories of elements they contain, including uranium, thorium, lutetium and hafnium.

Dauphas and Pourmand analyzed the abundances of these elements in more than 30 chondrites, and compared those to the compositions of another 20 martian meteorites.

"Once you solve the composition of chondrites you can address many other questions," Dauphas said.

Hafnium and thorium both are refractory or non-volatile elements, meaning that their compositions remain relatively constant in meteorites.

They also are lithophile elements, those that would have stayed in the mantle when the core of Mars formed. If scientists could measure the hafnium-thorium ratio in the martian mantle, they would have the ratio for the whole planet, which they need to reconstruct its formation history.

The relationships between hafnium, thorium and tungsten dictated that the hafnium-thorium ratio in the mantle of Mars must be similar to the same ratio in chondrites.

To derive the martian mantle's hafnium-tungsten ratio, they divided the thorium-tungsten ratio of the martian meteorites by the thorium-hafnium ratio of the chondrites.

"Why do you do that? Because thorium and tungsten have very similar chemical behavior," Dauphas said.

Once Dauphas and Pourmand had determined this ratio, they were able to calculate how long it took Mars to develop into a planet.

A computer simulation based on these data showed that Mars must have reached half its present size only two million years after the formation of the solar system.

"New application of radiogenic isotopes to both chondrite and martial meteorites provides data on the age and mode of formation of Mars," said Enriqueta Barrera, program director in NSF's Division of Earth Sciences. "That is consistent with models that explain Mars' small mass in comparison to that of Earth."

A quickly-forming Mars would help explain the puzzling similarities in the xenon content of its atmosphere and that of Earth's.

"Maybe it's just a coincidence, but maybe the solution is that part of the atmosphere of Earth was inherited from an earlier generation of embryos that had their own atmospheres, maybe a Marslike atmosphere," Dauphas said.

The short formation history of Mars further raises the possibility that aluminum 26, which is known from meteorites, turned the red planet into a magma ocean early in its history.

Aluminum 26 has a half-life of 700,000 years, so it would have disappeared too quickly to contribute to the internal heat of Earth.

If Mars formed in two million years, however, significant quantities of aluminum 26 would remain. "When aluminum 26 decays it releases heat and can completely melt the planet," Pourmand said.

The research was also funded by the National Aeronautics and Space Administration and the Packard Foundation.

Media Contacts
Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov
Steve Koppes, U. of Chicago (773) 702-8366 skoppes@chicago.edu
Barbra Gonzalez, RSMAS (305) 421-4704 barbgo@rsmas.miami.edu
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2010, its budget is about $6.9 billion. NSF funds reach all 50 states through grants to nearly 2,000 universities and institutions. Each year, NSF receives over 45,000 competitive requests for funding, and makes over 11,500 new funding awards. NSF also awards over $400 million in professional and service contracts yearly.

Cheryl Dybas | EurekAlert!
Further information:
http://www.nsf.gov
http://nsf.gov/news/news_summ.jsp?cntn_id=119590&org=NSF&from=news

More articles from Physics and Astronomy:

nachricht Hope to discover sure signs of life on Mars? New research says look for the element vanadium
22.09.2017 | University of Kansas

nachricht Calculating quietness
22.09.2017 | Forschungszentrum MATHEON ECMath

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>