New evidence links comet water to Earth’s oceans

Dec. 4 () –

A reinterpretation of data from the ESA Rosetta mission indicates that the water from comet 67P/Churyumov-Gerasimenko has a molecular signature similar to that of Earth’s ocean water.

Contradicting some recent results, this finding reopens the possibility that Jupiter family comets like 67P They could have helped bring water to Earth.

Water was essential for life to form and flourish on Earth and remains essential for life on Earth today. While some water likely existed in the gas and dust from which our planet materialized about 4.6 billion years ago, much of the water would have vaporized because Earth formed near the intense heat of the sun. How the Earth finally became rich in liquid water has continued to be a source of debate for scientists.

Research has shown that some of the Earth’s water originated from steam emitted by volcanoes; That vapor condensed and fell as rain on the oceans. But scientists have found evidence that a substantial part of our oceans came from ice and minerals from asteroids, and possibly comets, that collided with Earth. A wave of collisions of comets and asteroids with the inner planets of the solar system 4 billion years ago would have made this possible.

While the connection between asteroid water and Earth’s water is strong, the role of comets has baffled scientists. Several measurements of Jupiter-family comets (which contain primitive material from the early solar system and are thought to have formed beyond Saturn’s orbit) showed a strong link between their water and that of Earth. This link was based on a key molecular signature that scientists use to trace the origin of water throughout the solar system.

This signature is the ratio of deuterium (D) to regular hydrogen (H) in the water of any object, and it gives scientists clues about where that object formed. Deuterium is a rare and heavier type (or isotope) of hydrogen. When compared to water on Earth, This ratio of hydrogen in comets and asteroids may reveal whether there is a connection.

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

Measurements over the past two decades of deuterium in the water vapor of several other Jupiter-family comets showed levels similar to those in Earth’s water.

“It was really starting to look like these comets played an important role in providing water to Earth,” he said. in a statement Kathleen Mandt, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Mandt led the research, published in Science Advances, which reviewed the abundance of deuterium in 67P.

TOO MUCH DEUTERIUM

But in 2014, ESA’s (European Space Agency) Rosetta mission to 67P challenged the idea that Jupiter-family comets help fill Earth’s water reservoir. Scientists who analyzed Rosetta’s water measurements found the highest concentration of deuterium of any comet, and approximately three times more deuterium than there is in Earth’s oceanswhich have approximately one deuterium atom for every 6,420 hydrogen atoms.

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

Mandt’s team decided to use an advanced statistical calculation technique to automate the laborious process of isolating deuterium-rich water in more than 16,000 Rosetta measurements. Rosetta made these measurements in the “coma” of gas and dust surrounding 67P. Mandt’s team, which included scientists from Rosetta, was the first to analyze all European mission water measurements spanning the entire mission.

The researchers wanted to understand what physical processes caused the variability in the hydrogen isotope ratios measured in comets. Laboratory studies and observations of comets showed that cometary dust could affect readings of the amount of hydrogen that scientists detect in the comet’s vaporwhich could change our understanding of where the comet’s water comes from and how it compares to water on Earth.

“I was curious if we could find evidence of that happening on 67P,” Mandt said. “And this is just one of those very rare cases where a hypothesis is proposed and it’s actually found to happen.”

In fact, Mandt’s team found a clear connection between measurements of deuterium 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 they may not be representative of the composition of a comet’s body.

As a comet moves in its orbit closer to the sun, its surface heats up, causing gas to be released from the surface, including dust with chunks of water ice. Deuterium water sticks to dust grains more easily than regular water, research suggests. When ice from these dust grains is released into the coma, This effect could make the comet appear to have more deuterium than it does.

Mandt and his team reported that by the time the dust reaches the outer part of the coma, at least 120 kilometers from the body of the comet, it is already dry. Once the deuterium-rich water is gone, a space probe can precisely measure the amount of deuterium coming from the comet’s body.

This finding, say the authors of the article, has big implications not only to understand the role of comets in providing water to Earth, but also to understand the observations of comets that provide information about the formation of the early solar system.

“This means there is a great opportunity to review our past observations and prepare for future ones, so we can better explain the effects of dust,” Mandt said.