This implies that terrestrial planets, including Earth, have similar water sources--chondritic meteorites. However, unlike on Earth, Martian rocks that contain atmospheric volatiles such as water, do not get recycled into the planet's deep interior. Their work will be published in the December 1 issue of Earth and Planetary Science Letters. It is available online.
Much controversy surrounds the origin, abundance and history of water on Mars. The sculpted channels of the Martian southern hemisphere speak loudly of flowing water, but this terrain is ancient. Consequently, planetary scientists often describe early Mars as "warm and wet" and current Mars as "cold and dry."
Debate in the scientific community focuses on how the interior and crust of Mars formed, and how they differ from those of Earth. To investigate the history of Martian water and other volatiles, scientists at NASA's Johnson Space Center in Houston, Carnegie, and the Lunar and Planetary Institute in Houston studied water concentrations and hydrogen isotopic compositions trapped inside crystals within two Martian meteorites. The meteorites, called shergottites, were of the same primitive nature, but one was rich in elements such as hydrogen, whereas the other was depleted.
The meteorites used in the study contain trapped basaltic liquids, and are pristine samples that sampled various Martian volatile element environments. One meteorite appears to have changed little on its way from the Martian mantle up to the surface of Mars. It has a hydrogen isotopic composition similar to that of Earth. The other meteorite appears to have sampled Martian crust that had been in contact with the Martian atmosphere. Thus, the meteorites represent two very different sources of water. One sampled water from the deep interior and represents the water that existed when Mars formed as a planet, whereas the other sampled the shallow crust and atmosphere.
"There are competing theories that account for the diverse compositions of Martian meteorites," said lead Tomohiro Usui. "Until this study there was no direct evidence that primitive Martian lavas contained material from the surface of Mars."
Because the hydrogen isotopic compositions of the two meteorites differ, the team inferred that martian surface water has had a different geologic history than Martian interior water. Most likely, atmospheric water has preferentially lost the lighter hydrogen isotope to space, and has preferentially retained the heavier hydrogen isotope (deuterium).
That the enriched meteorite has incorporated crustal and atmospheric water could help to solve an important mystery. Are Martian meteorites that are enriched in components, such as water, coming from an enriched, deep mantle, or have they been overprinted by interaction with the Martian crust?
"The hydrogen isotopic composition of the water in the enriched meteorite clearly indicates that they have been overprinted, so this meteorite tells scientists more about the Martian crust than about the Martian mantle," Alexander said. "Conversely, the other meteorite yields more information about the Martian interior."
The concentrations of water in the meteorites are also very different. One has a rather low water concentration and that means that the interior of Mars is rather dry. Conversely, the enriched basalt has 10 times more water than the other one, suggesting that the surface of Mars could have been very wet at one time. Therefore, scientists are now starting to learn which meteorites tell us about the Martian interior and which samples tell us about the Martian surface.
"To understand the geologic history of Mars, more information about both of these environments is needed," Alexander said.
This workwas supported by a NASA Mars Fundamental Research Program grant, a NASA Cosmochemistry Program grant, and by a Astrobiology Institute grant ..
The Carnegie Institution for Science is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
Conel Alexander | EurekAlert!
Successful Boron-Doping of Graphene Nanoribbon
27.08.2015 | Universität Basel
New theory leads to radiationless revolution
27.08.2015 | Australian National University
A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).
Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African...
In mountainous regions earthquakes often cause strong landslides, which can be exacerbated by heavy rain. However, after an initial increase, the frequency of these mass wasting events, often enormous and dangerous, declines, in fact independently of meteorological events and aftershocks.
These new findings are presented by a German-Franco-Japanese team of geoscientists in the current issue of the journal Geology, under the lead of the GFZ...
Bacteria do not cease to amaze us with their survival strategies. A research team from the University of Basel's Biozentrum has now discovered how bacteria enter a sleep mode using a so-called FIC toxin. In the current issue of “Cell Reports”, the scientists describe the mechanism of action and also explain why their discovery provides new insights into the evolution of pathogens.
For many poisons there are antidotes which neutralize their toxic effect. Toxin-antitoxin systems in bacteria work in a similar manner: As long as a cell...
It comes when called, bringing care utensils with it and recording how they are used: Fraunhofer IPA is developing an intelligent care cart that provides care staff with physical and informational support in their day-to-day work. The scientists at Fraunhofer IPA have now completed a first prototype. In doing so, they are continuing in their efforts to improve working conditions in the care sector and are developing solutions designed to address the challenges of demographic change.
Technical assistance systems can improve the difficult working conditions in residential nursing homes and hospitals by helping the staff in their work and...
Since the opening of the Suez Canal in 1869 many hundreds of marine animal and plant species from the Red Sea have invaded the eastern Mediterranean, leading...
20.08.2015 | Event News
20.08.2015 | Event News
19.08.2015 | Event News
27.08.2015 | Life Sciences
27.08.2015 | Health and Medicine
27.08.2015 | Health and Medicine