New data collected by Rosetta, the European Space Agency’s (ESA) robotic probe raises questions about the validity of a previous theory that suggests water was brought to Earth by comets impacting its surface in the early days of our solar system creation.
ESA’s probe did several tests and found out that the type of water present on comet 67P/ Churyumov-Gerasimenko was different from water on Earth. This means that comets did not bring water to Earth.
Up till now, scientists believed that Earth had to cool down 4.6 billion years ago in order to allow water rich comets and asteroids bring water to its surface. Scientists say that before that moment Earth was so hot that any water brought to it would have instantly boiled off leaving Earth a lifeless planet.
Due to Rosetta’s results researchers now believe that the main carriers of water to Earth were in fact asteroids.
“We knew that Rosetta’s in situ analysis of this comet was always going to throw up surprises for the bigger picture of solar system science, and this outstanding observation certainly adds fuel to the debate about the origin of Earth’s water,”
Matt Taylor, researcher for the Rosetta Mission, said.
Rosetta probe landed on comet 67P in August. A month later, the probe’s scientific instruments revealed that water vapor streaming away from this space object’s body was not matching the samples of water collected from Earth’s oceans.
ESA scientists said they were able to tell if the water samples matched by the water’s “flavor” called deuterium. Deuterium or “heavy water” is a hydrogen molecule with an extra neutron. Rosetta measured the proportion of deuterium to normal hydrogen in both water samples. This ratio can give some answers about how water got to Earth since this ratio has different values according to the time and location where a comet was formed.
The ROSINA scientific tool used by Rosetta to measure this ratio revealed that water from 67P had a Deuterium-Hydrogen ratio three times higher than Earth’s water.
Other space probes and telescopes analyzed the D/H water ratios from samples collected on 11 comets and tried to give an answer to the origin of Earth’s water issue. Only one comet had water similar like the one on Earth.
In 2011, Herschel telescope analyzed comet 103P/Hartley 2 and found out that its water’s D/H ratio was very close to Earth’s water ratio. This was a surprise for the scientific community because everybody expected that this comet would have higher values of D/H since it was a Jupiter-family comet.
In 1986, ESA’s Giotto probe analyzed the D/H ratio of the water present on comet Halley. Halley had twice as much deuterium in its water than Earth. Back then, scientists believed that Halley-like comets were the source of our oceans.
This week, Rosetta revealed that the Jupiter-family 67P comet has the highest D/H ratio of the comets ever measured.