A new study of comet 67P suggests that the comet’s water may be similar to that of Earth, contradicting earlier findings from the Rosetta mission that showed high levels of deuterium. This suggests that comets may have played a role in providing water to Earth, as the effects of dust in earlier measurements may have skewed the results.

Origin of water on earth

Scientists have discovered that the water on comet 67P/Churyumov-Gerasimenko shares a molecular signature with water in Earth’s oceans. The discovery casts doubt on recent research and brings back the theory that Jupiter family comets such as 67P may have played a role in bringing water to Earth.

Water has always been crucial to life on Earth, both in terms of its formation and continued existence. Although some water formed in the gas and dust cloud that gave birth to our planet 4.6 billion years ago, most of it evaporated due to the overheating of the Sun in the early days of the Earth. How such amounts of liquid water appeared on Earth has long been a subject of scientific debate.

The role of comets and asteroids

Research shows that some of the water on Earth is formed as a result of volcanic activity, and the water vapor released by explosions condenses and falls as rain, filling the oceans. But evidence also suggests that most of Earth’s water comes from ice and minerals carried by asteroids and possibly comets that hit the planet. About 4 billion years ago, a period of frequent collisions of asteroids and comets with the Solar System’s inner planets may have significantly affected Earth’s water supply.

While the evidence for a connection between asteroid water and terrestrial water is compelling, the role of comets has puzzled scientists. Various measurements made on Jupiter family comets, which contain primitive material from the early Solar System and are thought to have formed in the orbit of Saturn, have shown a close relationship between their water and that of Earth. This connection was based on a key molecular signature that scientists used to determine the origin of water in the Solar System.

Examination of deuterium rate

This signature is the ratio of deuterium (D) to ordinary hydrogen (H) in the water of any object and gives scientists clues as to where the object was formed. Deuterium is a rarer, heavier form or isotope of hydrogen. This ratio of hydrogen in comets and asteroids compared to water on Earth could reveal whether there is a connection. Because deuterium-containing water is more likely to form in cold environments, objects that form farther from the Sun, such as comets, have higher isotope concentrations than objects that form closer to the Sun, such as asteroids.

Re-evaluation of Comet’s water additives

Measurements of deuterium in the water vapor of several other comets in the Jupiter family over the past few decades have shown levels similar to water on Earth.

“It was starting to look like these comets were playing a really important role in bringing water to Earth,” said Kathleen Mandt, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Mandt led the study, published on: Science Developments November 13 looks at the deuterium content of 67P.

A new understanding of Rosetta results

But in 2014, ESA’s (European Space Agency) Rosetta mission to 67P cast doubt on the idea that Jupiter family comets help replenish Earth’s water supply. Analyzing Rosetta’s water measurements, scientists found the highest concentration of deuterium of any comet and nearly three times more deuterium than Earth’s oceans, where there is 1 deuterium atom for every 6,420 hydrogen atoms.

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

Mandt’s team decided to use advanced statistical computing to automate the time-consuming process of deuterium-rich extraction. More than 16,000 Rosetta measurements of water. Rosetta made these measurements in a “coma” of gas and dust around 67P. Mandt’s team, which included Rosetta scientists, was the first to analyze all of the European mission’s water measurements spanning the entire mission.

Implications and future research

The researchers wanted to understand what physical processes caused the variability in hydrogen isotope ratios measured in comets. Laboratory studies and comet observations have shown that comet dust can affect the proportions of hydrogen that scientists detect in comet pairs, which could change our understanding of where comet water comes from and how it compares to water on Earth.

“So I was wondering if we could find evidence that this happened on 67P,” Mandt said. “And this is just one of those very rare cases where you put forward a hypothesis and see it actually happen.”

In fact, Mandt’s team found a clear correlation between deuterium measurements in the 67P coma and the amount of dust around the Rosetta spacecraft; This showed that measurements taken near the spacecraft, in parts of the coma, may not reflect the comet’s composition. body.

As the comet approaches the Sun in its orbit, its surface heats up, resulting in the release of gas from the surface, including dust and fragments of water ice. Research shows that deuterium water adheres to dust particles more easily than regular water. When the ice on these dust particles falls into a coma, this effect can cause the comet to have more deuterium than it actually has.

Mandt and his team reported that the dust would have dried by the time it reached the outer part of the coma, at least 75 miles from the comet’s body. Once the deuterium-rich water disappears, the spacecraft will be able to accurately measure the amount of deuterium coming from the comet’s body. The paper’s authors say this discovery is important not only for understanding the role of comets in bringing water to Earth, but also for understanding comet observations that shed light on the formation of the early solar system.

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