New Study Challenges Previous Findings, Suggesting Comets May Have Contributed to Earth’s Water.

This image, captured by ESA’s Rosetta navigation camera on March 14, 2015, from about 53 miles away from Comet 67P/Churyumov-Gerasimenko, has a resolution of 24 feet per pixel and is cropped and processed to highlight the comet’s activity.

A breakthrough study led by NASA’s Kathleen Mandt has reignited the debate over the origins of Earth’s water, revealing that the water on Comet 67P/Churyumov–Gerasimenko has a molecular signature strikingly similar to Earth’s ocean water. This finding revises previous conclusions and reopens the case that Jupiter-family comets like 67P could have been instrumental in delivering water to Earth.

Water is a fundamental component for life, and its origins on Earth have been a long-standing scientific puzzle. While some researchers have suggested that volcanic activity provided much of the Earth’s early water, others have pointed to asteroids and comets as key contributors. A recent surge in cometary studies, particularly focusing on Jupiter-family comets, has brought new insights into this debate.

The key to tracing the origins of water lies in a molecular signature involving deuterium, a heavy isotope of hydrogen. Water formed far from the Sun, such as on comets, tends to have a higher ratio of deuterium to regular hydrogen due to the colder conditions in the outer solar system. Initially, measurements of Jupiter-family comets, which are thought to have formed beyond Saturn’s orbit, revealed that their water had a deuterium ratio comparable to Earth’s. This raised the possibility that these comets played a crucial role in Earth’s water delivery during the early solar system.

However, this theory was questioned after the European Space Agency’s Rosetta mission to Comet 67P in 2014. Data from Rosetta suggested that 67P’s water contained much higher levels of deuterium than Earth’s oceans, challenging the idea that comets were the main source of Earth’s water.

Mandt and her team decided to revisit these measurements, using advanced statistical techniques to reassess Rosetta’s data. The team analyzed over 16,000 measurements of the comet’s water, revealing that dust particles around the comet might have skewed the results. As the comet moves closer to the Sun, heat causes ice to vaporize, releasing water that clings to dust particles. This process results in deuterium-rich water sticking to the dust, which could explain the elevated deuterium readings recorded by Rosetta.

Mandt’s team found that when dust-laden measurements were removed, the data showed a much more Earth-like deuterium ratio. This suggests that the comet’s water, once corrected for the dust effect, could indeed share a similar signature with Earth’s water.

This discovery has significant implications for both understanding the role of comets in Earth’s water supply and for future cometary research. It also opens up new possibilities for revisiting previous comet data and refining techniques for analyzing comet compositions, providing a clearer picture of the solar system’s early history.

“This means there is a great opportunity to revisit our past observations and prepare for future ones so we can better account for the dust effects,” Mandt said. This revelation could be a major step forward in understanding the solar system’s formation and the crucial role of comets in shaping Earth’s water-rich environment.