Early accretion of water in the inner solar system from a carbonaceous chondrite–like source

Adam R. Sarafian

Determining the origin of water and the timing of its accretion 
within the inner solar system is important for understanding 
the dynamics of planet formation....
The timing of water accretion to the inner solar system also has implications 
for how and when life emerged on Earth. 
We report in situ measurements of the hydrogen isotopic composition 
of the mineral apatite in eucrite meteorites, whose parent body is the 
main-belt asteroid 4 Vesta. 
These measurements sample one of the oldest hydrogen reservoirs in 
the solar system and show that Vesta contains the same hydrogen isotopic composition as that of carbonaceous chondrites. 
Taking into account the old ages of eucrite meteorites and their 
similarity to Earth’s isotopic ratios of hydrogen, carbon, and nitrogen, 
we demonstrate that these volatiles could have been added early to Earth, 
rather than gained during a late accretion event.

sciencemag.org