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NASA: Mars formed from similar building blocks to those of Earth

Mars formed from similar building blocks to that of Earth, according to Carnegie Institution for Science. NASA scientists, including Carnegie’s Conel Alexander and Jianhua Wang, examined the hydrogen in water from the Martian interior and came to this conclusion. The scientists note, however, that there were several differences in the later evolution of Mars and Earth.

Their finding suggests that Earth-like planets have similar water sources (chondritic meteorites). The scientists say, however, that Martian rocks that contain water do not get recycled into the planet’s deep interior.

Scientists are still arguing the details of water on Mars. Scientists, for example, call early Mars “warm and wet” because sculpted channels in the ancient terrain of the Martian southern hemisphere are perfect for flowing water. Scientists, however, call current Mars “cold and dry.”

To put to rest debate in the scientific community over how the interior and crust of Mars formed, scientists at NASA’s Johnson Space Center, Carnegie and the Lunar and Planetary Institute examined water concentrations and hydrogen isotopic compositions stuck inside crystals within two Martian meteorites. One meteorite, scientists report, was rich in elements whereas the other was depleted.

Scientist contend that the meteorites contain trapped basaltic liquids. One meteorite, the report notes, changed little on its way from the Martian mantle up to the surface of Mars. That particular meteorite has a hydrogen isotopic composition that is similar to that of Earth. The second meteorite, on the other hand, looks like it may have sampled Martian crust that had been in contact with the Martian atmosphere. The meteorites, scientists say, correspond to two different sources of water. One meteorite represents that water from early Mars and the other meteorite sampled the shallow crust and atmosphere.

“There are competing theories that account for the diverse compositions of Martian meteorites,” says lead scientist Tomohiro Usui. “Until this study there was no direct evidence that primitive Martian lavas contained material from the surface of Mars.”

Scientists believe that the martian surface water has had a much different geologic history than Martian interior water. The meteorite that sampled the shallow crust and atmosphere probably lost the lighter hydrogen isotope to space, while retaining the heavier hydrogen isotope.

“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,” Mr. Alexander said. “Conversely, the other meteorite yields more information about the Martian interior.”

Scientists also say that one meteorite has a low water concentration, meaning that the interior of Mar is dry. The enriched one, however, suggests that the surface of Mars could have been very wet at one time. Scientists will continue to study these meteorites to understand which meteorites tell us about the Martian interior and which ones tell us about the Martian surface.

“To understand the geologic history of Mars, more information about both of these environments is needed,” Mr. Alexander said.

The study’s findings will be detailed in the December 1 issue of Earth and Planetary Science Letters.