Despite conflicting with the results of some recent studies, this new discovery reinforces the claim that Jupiter-based comets like 67P/Churyumov-Gerasimenko may have contributed to providing water to Earth. This finding has been confirmed.
This pseudocolor four-image mosaic consists of images taken on February 3, 2015, from a distance of 28.7 km from the center of comet Churyumov-Gerasimenko. The size of the mosaic is 4.2 x 4.6 km. Image credit: ESA / Rosetta / NAVCAM / CC BY-SA IGO 3.0.
Water is crucial for the formation and sustenance of life on Earth, and continues to be central to life on Earth today.
It is believed that some water was present in the gas and dust that formed our planet around 4.6 billion years ago, but due to Earth forming close to the sun’s intense heat, a considerable amount of water is thought to have evaporated.
The process by which Earth became abundant in liquid water is still a subject of debate among scientists.
Studies have indicated that a portion of Earth’s water originates from steam released by volcanoes, which then condensed and fell into the oceans.
Furthermore, evidence suggests that a significant percentage of our oceans resulted from the impact of ice and minerals from asteroids and potentially comets hitting Earth.
A series of comets and asteroids colliding with inner solar system planets 4 billion years ago could have facilitated this occurrence.
While there is a strong theory linking asteroid water to Earth’s water, the role of comets has perplexed scientists.
Multiple measurements of Jupiter-based comets have indicated a strong correlation between their water and that of Earth.
This connection is based on a fundamental molecular signature utilized by scientists to track the origins of water across the solar system.
The deuterium (D) to ordinary hydrogen (H) ratio in an object’s water serves as this signature, providing insights into the object’s formation location.
By comparing this hydrogen ratio in comets and asteroids to that of Earth’s water, scientists can discern a potential connection.
Deuterium-rich water is more likely to form in cold environments, resulting in objects formed farther from the Sun, such as comets, exhibiting higher concentrations of this isotope compared to objects formed nearer to the Sun, like asteroids.
Measurements conducted over the past few decades on the deuterium in the water vapor of various other Jupiter-based comets have revealed levels akin to Earth’s water.
“It seems increasingly likely that these comets play a significant role in delivering water to Earth,” commented Dr. Kathleen Mandt, a planetary scientist at NASA Goddard Space Flight Center.
However, ESA’s Rosetta mission to 67P/Churyumov-Gerasimenko in 2014 challenged the notion that Jupiter-based comets aid in replenishing Earth’s water reservoirs.
Upon analyzing Rosetta’s water measurements, scientists discovered that it has the highest deuterium concentration among all comets, with approximately 100% more deuterium than Earth’s oceans (about 1 deuterium atom for every 6,420 hydrogen atoms), surpassing it by threefold.
“This was a significant revelation that compelled us to reassess everything,” remarked Dr. Mandt.
An advanced statistical computing approach was employed by the researchers to automate the laborious task of segregating deuterium-rich water from over 16,000 Rosetta measurements.
These measurements were taken within the gas and dust coma encircling 67P/Churyumov-Gerasimenko by Rosetta.
For the first time, Dr. Mandt and collaborators analyzed all water measurements from the European mission.
The researchers aimed to comprehend the physical processes influencing the fluctuations in hydrogen isotope ratios detected in comets.
Studies on comet dust in laboratory settings and observations indicated that comet dust could impact the hydrogen proportion detected in comet vapors, potentially altering how the comet’s water compares to Earth’s water.
“So, I was curious to see if I could find evidence of this phenomenon occurring in 67P/Churyumov-Gerasimenko,” added Dr. Mandt.
“This is one of those rare instances where a hypothesis is proposed and genuinely validated.”
In fact, scientists identified a distinct correlation between the deuterium measurements of 67P/Churyumov-Gerasimenko within its coma and the amount of surrounding dust near the Rosetta spacecraft, indicating that measurements taken in certain regions of the coma near 67P/Churyumov-Gerasimenko may not accurately represent the comet’s celestial composition.
As the comet traverses an orbit closer to the Sun, its surface warms, releasing gases from the surface, including dust particles with attached water ice fragments.
Research suggests that water containing deuterium has a higher tendency to adhere to dust particles compared to regular water.
When this ice on dust particles is expelled into a coma, it can create an illusion of the comet containing more deuterium than it actually does.
The researchers noted that by the time the dust reaches the outer regions of the coma, at least 120 miles away from the comet’s core, the coma depletes of water.
Once the deuterium-rich water dissipates, the spacecraft can precisely measure the amount of deuterium emanating from the comet’s core.
“This discovery holds profound implications not only for elucidating the role of comets in supplying water to Earth but also for comprehending comet observations that offer insights into the early solar system’s formation,” the researchers noted.
“This discovery provides a unique opportunity to revisit previous observations and prepare for future observations to better factor in the effects of dust.”
of study Published in a magazine scientific progress.
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Kathleen E. Mandt others. 2024. D/H of comet 67P/Churyumov-Gerasimenko almost on Earth. scientific progress 10(46);doi: 10.1126/sciadv.adp2191
