There's also a growing understanding that rocky planets form with a primordial envelope rich in hydrogen and helium that they acquire from their solar nebulae.
The comet is blasting out water at a rate of about 40 kilograms per second while still far from the Sun—much farther than where most comets “switch on.”
Contradicting the results of several recent studies, the new findings reopen the case that Jupiter-family comets like 67P/Churyumov-Gerasimenko could have helped deliver water to Earth.
