New research suggests Earth got most of its water from asteroid impacts over 4.6 billion years ago, around the time planets were forming, conflicting with earlier beliefs that water was supplied to Earth when the planet was being bombarded with meteorites between 4.1 billion and 3.8 billion years ago. Either way, water originated from an outside source, and has been around for a very, very long time.
While studying a meteorite that fell to Earth back in 2000, researchers concluded that the space rock’s parent asteroid lost its water soon after forming. They were able to determine this by using a transmission electron microscope, which was used to study the rock’s magnetite particles. The find is important to note because it means meteorites that hit the Earth several hundred million years after our planet was formed were completely dry. The meteorite itself is believed to have originated from the main belt between Mars and Jupiter.
According to Yuki Kimura, of Tohoku University in Japan, the presence of colloidal crystal was telling because it helped him and his team determine when the meteorite’s parent asteroid water disappeared. While Kimura’s findings don’t change the opinion that water on Earth came from very early impacts, the new data suggests one of the most fundamental compounds for life arrived a lot sooner than previously thought.