Comet 67P’s water is the same as Earth’s oceans

A team of NASA researchers has discovered that water from comet 67P/Churyumov-Gerasimenko has a molecular signature similar to water in Earth’s oceans.

The discovery of a molecular signature in comet 67/P’s water similar to that in Earth’s water reopens the hypothesis that Jupiter-family comets, like this one, may have helped to bring water to Earth.

Water was essential for life to form and flourish on Earth and continues to be fundamental to current terrestrial life.

Although it was likely that there was some water in the gas and dust from which our planet materialized about 4.6 billion years ago, much of the water would have vaporized because the Earth formed near the intense heat of the Sun.

How Earth Became Rich in Liquid Water continues to be a source of debate for scientists. Some studies have shown that some of Earth’s water has had originating from the steam released by volcanoes; this vapor condensed and rained into the oceans.

But scientists have also discovered evidence that a substantial part of our oceans comes from the ice and minerals of asteroidsand possibly from comets, which collided with Earth.

A wave of comet and asteroid collisions with the inner planets of the Solar System 4 billion years ago would have made this possible. Although the link between water on asteroids and that on Earth is strong, the role of comets has puzzled scientists.

Several measurements of Jupiter family comets – which contain primitive material from the early Solar System and are thought to have formed beyond the orbit of Saturn – showed a strong connection between its water and that of the Earth.

This connection is based on a key molecular signature that scientists use to track the source of water throughout the Solar System. This specific signature is the ratio between deuterium (D) and normal hydrogen (H) in the water of any object, and gives scientists clues about where that object formed.

O deuterium is a rare and heavier type – or isotope – of hydrogen. When compared to Earth’s water, this proportion of hydrogen in comets and asteroids can reveal whether a bond exists.

Because deuterium-containing water is more likely to form in cold environments, there is a greater concentration of the isotope in objects that formed far from the Sun, such as comets, than in objects that formed closer to the Sunlike asteroids.

Measurements, made over the last two decades, of deuterium in the water vapor of several other comets in the Jupiter family revealed similar levels to those of Earth’s water.

“It was starting to look like these comets were playing an important role in transporting water to Earth,” he said. Kathleen Mandtplanetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Mandt led the study, the results of which were presented in a November issue of Science Advanceswhich reviews the abundance of deuterium do not commit 67P.

In 2014, the European Space Agency/ESA, which led to , challenged the idea that Jupiter-family comets helped fill Earth’s water reservoir.

Scientists who analyzed water measurements taken by Rosetta found the highest concentration of deuterium of any comet and about three times more deuterium than in Earth’s oceans, which have about 1 deuterium atom for every 6,420 hydrogen atoms.

“It was a big surprise and made us rethink everything“, said Mandt.

Mandt’s team decided to use an advanced statistical computing technique to automate the laborious process of isolating deuterium-rich water from more than 16,000 Rosetta measurements.

Rosetta performed these measurements on the “hair” of gas and dust that surrounds comet 67P. Mandt’s team, which included Rosetta scientists, was the first to analyze all of the European mission’s water measurements over the entire mission.

Researchers wanted to understand what physical processes caused the variability in hydrogen isotope ratios measures you commit to us.

Laboratory studies and observations of comets have shown that cometary dust he can affect hydrogen ratio readings that scientists detect in the comet’s vapor, which could change our understanding of the origin of the comet’s water and its comparison with Earth’s water.

“That’s why, I was curious to know if we could find evidence that this happened on comet 67P,” said Mandt. “And this is one of those very rare cases where propose a hypothesis and discover that it is actually happening“.

In fact, Mandt’s team found a clear connection between deuterium measurements in the 67P coma and the amount of dust around the Rosetta spacecraft, showing that measurements taken near the spacecraft in some parts of the coma may not be representative of the composition of the comet’s body.

As a comet moves in its orbit closer to the Sun, its surface heats upcausing the release of gas from the surface, including dust with bits of water ice.

Water with deuterium adheres more easily to dust grains than regular water, research suggests. When the ice from these dust grains is released into the hair, this effect can make the comet appear to have more deuterium of what you have.

Mandt and his team emphasize that when the dust reaches the outer part of the coma, at least 120 kilometers from the comet’s body, it’s already dry. With the deuterium-rich water gone, a spacecraft can accurately measure the amount of deuterium coming from the comet’s body.

This discovery, the study authors say, has major implications not only for understanding the role of comets in supplying Earth with water, but also for understanding observations of comets that provide information about the formation of the early Solar System.

“This means there is a great opportunity to review our previous observations and prepare for future ones so that we can take the effects of dust into account,” Mandt said.