Water. All life on Earth requires it in some way or another, and it's hard to miss that roughly 70% of our planet's surface is covered in the stuff. Thus, understanding where Earth's water came from is a very important part of understanding life's origins, and researchers were pretty sure they knew how it got here — up until 2014.
Basically, scientists previously believed that Earth's liquid reservoirs arrived here on icy asteroids and comets from the outer regions of the solar system during the early stages of Earth's formation. However, a 2014 analysis of the molecular constituents of water on the comets that likely seeded Earth's water cast doubt on the hypothesis.. And now, the researchers think they know why their analysis of water on these icy bodies posed such a conflict.
