In new research, planetary scientists from the University of Maryland and elsewhere analyzed melted meteorites that had been floating around in space since the Solar System’s formation around 4.5 billion years ago. They found that these meteorites had extremely low water content — in fact, they were among the driest extraterrestrial materials ever measured. This finding implies that substantial amounts of water could only have been delivered to Earth by means of unmelted, or chondritic, meteorites.
“We wanted to understand how our planet managed to get water because it’s not completely obvious,” said University of Maryland researcher Megan Newcombe and colleagues.
“Getting water and having surface oceans on a planet that is small and relatively near the sun is a challenge.”
Dr. Newcombe and co-authors analyzed seven melted, or achondrite, meteorites that crashed into Earth billions of years after splintering from at least five planetesimals — objects that collided to form the planets in our Solar System.
In a process known as melting, many of these planetesimals were heated up by the decay of radioactive elements in the early Solar System’s history, causing them to separate into layers with a crust, mantle and core.
Because these meteorites fell to Earth only recently, this experiment was the first time anyone had ever measured their volatiles.
“The challenge of analyzing water in extremely dry materials is that any terrestrial water on the sample’s surface or inside the measuring instrument can easily be detected, tainting the results,” said Dr. Conel Alexander, a scientist at the Carnegie Institution for Science.
To reduce contamination, the researchers first baked their samples in a low-temperature vacuum oven to remove any surface water.
Before the samples could be analyzed in the secondary ion mass spectrometer, the samples had to be dried out once again.
Some of the meteorite samples came from the inner solar system, where Earth…
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