Earth may have kept its own water rather

Carl Sagan famously dubbed Earth the “pale blue dot” for our planet’s abundant water. But where this water came from—and when it arrived—has been a longstanding debate. Many scientists argue that Earth formed as a dry planet, and gained its water millions of years later through the impact of water-bearing asteroids or comets. But now, scientists say that Earth may have had water from the start, inheriting it directly from the swirling nebula that gave birth to the solar system. If true, the results suggest that water-rich planets may abound in the universe.

However, researchers don’t really know the true hydrogen isotopic composition of Earth’s water, says Lydia Hallis, a planetary scientist at the University of Glasgow in the United Kingdom and lead author of the new study. Scientists have often assumed that the isotopic signature of seawater is close to the true value, but Hallis thinks this has probably changed over geologic time, as Earth preferentially lost light hydrogen atoms to space and gained water from asteroid and comet impacts.

So Hallis and her colleagues went looking for vestiges of the early Earth that might preserve the original hydrogen isotope ratio of the planet. They found them in an unlikely place: Baffin Island in the Canadian Arctic. Here, massive eruptions—fueled by the hot spot that now sits beneath Iceland—produced lava that originated deep in the mantle. So deep, in fact, that this material was probably isolated from the surface for almost all of Earth’s history. The evidence lies in the fact that the lavas, now hardened into basalts, still contain a fair amount of light helium isotopes, which would have escaped to space had the rocks spent much time anywhere near the surface.www.glorybios.com