Evidence of early history of Earth’s formation preserved in Mars

November 22nd, 2007 - 1:27 pm ICT by admin  

Washington, Nov 22 (ANI): A new study by scientists has indicated that the processes involved in the early history of Earth’s formation have been preserved in Mars.
According to the research conducted by NASA’s Johnson Space Center and the Lunar and Planetary Institute (LPI), the early histories of both Earth and Mars are complex and involve processes no longer observed. Evidence of these processes has been preserved in Mars, while it has been erased in Earth.
That means Mars is probably the best opportunity to understand how Earth formed.
Keeping this fact in mind, the research team performed precise measurements of neodymium isotope compositions of nine rare Martian meteorites called shergottites using mass spectrometers.
Shergottites, named after the first-identified meteorite specimen that fell at Shergotty, India, in 1865, are a group of related meteorites from Mars composed primarily of pyroxene and feldspar. They are a treasure chest of information about the red planet and have been the focus of extensive research by scientists. The scientists examined shergottites because their large range in chemical compositions is thought to be a fingerprint of the formation of their deep sources very early in the history of Mars.
“These rocks were lavas that were made by melting deep in Mars and then erupted on the surface,” said Alan Brandon from JSC. “They were delivered to Earth as meteorites following impacts on Mars that exhumed them and launched them into space,” he added.
As for the time period for the formation of the different shergottite, the research team was able to use two radiometric isotopes from the element samarium for the purpose.
“We expected to find that their sources all formed at the same time,” said Vinciane Debaille from LPI . “But what we found instead was that the shergottite sources formed at two different times. The oldest formed at 35 million years after the solar system began to condense from ice and dust into large planets about 4,567 million years ago. The youngest formed about 110 million years after the solar system began to condense,” he added.
The team found that the scenario that best fits the data is one where a global-scale magma ocean formed from melting in Mars during the final stages of accretion and then slowly solidified over this time period. The new data from the study also found out that terrestrial planets such as the Earth and Mars may have remained molten in their early histories for tens of millions of years. The findings indicate that the two planets cooled slower than scientists thought.
But scientists think that early crust formation alone cannot account for the slow cooling magma ocean seen in large planets.
This new evidence instead implies that Mars, at one time, had a primitive atmosphere that acted as the insulator.
“The primitive atmosphere was composed mostly of hydrogen left over from accretion into a rocky planet, but was removed, probably by impacts, about 100 million years after the planet formed,” said Vinciane Debaille from LPI.
“The most recent physical models for magma oceans suggest they solidify on timescales of a few million years or less, so this result is surprising,” said Brandon. “Some type of insulating blanket, either as a rocky crust or a thick atmosphere, is needed as an insulator to have kept the Martian interior hot,” he added. (ANI)

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