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By NASA
Scientists find that cometary dust affects interpretation of spacecraft measurements, reopening the case for comets like 67P as potential sources of water for early Earth.
Researchers have found that water on Comet 67P/Churyumov–Gerasimenko has a similar molecular signature to the water in Earth’s oceans. Contradicting some recent results, this finding reopens the case that Jupiter-family comets like 67P could have helped deliver water to Earth.
Water was essential for life to form and flourish on Earth and it remains central for Earth life today. While some water likely existed in the gas and dust from which our planet materialized around 4.6 billion years ago, much of the water would have vaporized because Earth formed close to the Sun’s intense heat. How Earth ultimately became rich in liquid water has remained a source of debate for scientists.
Research has shown that some of Earth’s water originated through vapor vented from volcanoes; that vapor condensed and rained down on the oceans. But scientists have found evidence that a substantial portion of our oceans came from the ice and minerals on asteroids, and possibly comets, that crashed into Earth. A wave of comet and asteroid collisions with the solar system’s inner planets 4 billion years ago would have made this possible.
This image, taken by ESA’s Rosetta navigation camera, was taken from a about 53 miles from the center of Comet 67P/Churyumov-Gerasimenko on March 14, 2015. The image resolution is 24 feet per pixel and is cropped and processed to bring out the details of the comet’s activity. ESA/Rosetta/NAVCAM While the case connecting asteroid water to Earth’s 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 link between their water and Earth’s. This link was based on a key molecular signature scientists use to trace the origin of water across 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, heavier type — or isotope — of hydrogen. When compared to Earth’s water, this hydrogen ratio in comets and asteroids can reveal whether there’s a connection.
Because water with deuterium is more likely to form in cold environments, there’s a higher concentration of the isotope on objects that formed far from the Sun, such as comets, than in objects that formed closer to the Sun, like asteroids.
Measurements within the last couple of decades of deuterium in the water vapor of several other Jupiter-family comets showed similar levels to Earth’s water.
“It was really starting to look like these comets played a major role in delivering water to Earth,” said Kathleen Mandt, planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Mandt led the research, published in Science Advances on Nov. 13, that revises the abundance of deuterium in 67P.
About Kathleen Mandt
But in 2014, ESA’s (European Space Agency) Rosetta mission to 67P challenged the idea that Jupiter-family comets helped fill Earth’s water reservoir. Scientists who analyzed Rosetta’s water measurements found the highest concentration of deuterium of any comet, and about three times more deuterium than there is in Earth’s oceans, which have about 1 deuterium atom for every 6,420 hydrogen atoms.
“It was a big surprise and it made us rethink everything,” Mandt said.
Mandt’s team decided to use an advanced statistical-computation 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 Rosetta scientists, was the first to analyze all of the European mission’s water measurements spanning the entire mission.
The researchers wanted to understand what physical processes caused the variability in the hydrogen isotope ratios measured at comets. Lab studies and comet observations showed that cometary dust could affect the readings of the hydrogen ratio that scientists detect in comet vapor, which could change our understanding of where comet water comes from and how it compares to Earth’s water.
What are comets made of? It’s one of the questions ESA’s Rosetta mission to comet 67P/Churyumov-Gerasimenko wanted to answer. “So I was just curious if we could find evidence for that happening at 67P,” Mandt said. “And this is just one of those very rare cases where you propose a hypothesis and actually find it happening.”
Indeed, Mandt’s team found a clear connection between deuterium measurements in the coma of 67P and the amount of dust around the Rosetta spacecraft, showing that the measurements taken near the spacecraft in some parts of the coma 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 warms up, causing gas to release from the surface, including dust with bits of water ice on it. Water with deuterium sticks to dust grains more readily than regular water does, research suggests. When the ice on these dust grains is released into the coma, this effect could make the comet appear to have more deuterium than it has.
Mandt and her team reported that by the time dust gets to the outer part of the coma, at least 75 miles from the comet body, it is dried out. With the deuterium-rich water gone, a spacecraft can accurately measure the amount of deuterium coming from the comet body.
This finding, the paper authors say, has big implications not only for understanding comets’ role in delivering Earth’s water, but also for understanding comet observations that provide insight into the formation of the early solar system.
“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.
By Lonnie Shekhtman
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Dec 03, 2024 Editor Lonnie Shekhtman Contact Lonnie Shekhtman lonnie.shekhtman@nasa.gov Location Goddard Space Flight Center Related Terms
Comets Goddard Space Flight Center Planetary Science Planetary Science Division Rosetta Science Mission Directorate The Solar System View the full article
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By European Space Agency
Video: 00:09:09 On 12 November 2014, after a ten-year journey through the Solar System and over 500 million kilometres from home, Rosetta’s lander Philae made space exploration history by touching down on a comet for the first time. On the occasion of the tenth anniversary of this extraordinary feat, we celebrate by taking a look back over the mission's highlights.
Rosetta was an ESA mission with contributions from its Member States and NASA. It studied Comet 67P/Churyumov-Gerasimenko for over two years, including delivering lander Philae to the comet’s surface. Philae was provided by a consortium led by DLR, MPS, CNES and ASI.
read the article Philae’s extraordinary comet landing relived.
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By European Space Agency
On 12 November 2014, after a ten year journey through the Solar System and over 500 million kilometres from home, Rosetta’s lander Philae made space exploration history by touching down on a comet for the first time. On the occasion of the tenth anniversary of this extraordinary feat, we celebrate Philae’s impressive achievements at Comet 67P/Churyumov-Gerasimenko.
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By European Space Agency
Video: 00:00:23 From 7 until 13 October 2024, ESA/NASA’s SOHO spacecraft recorded Comet C/2023 A3 (Tsuchinshan–ATLAS), the second brightest comet it has ever seen. Meanwhile, large amounts of material were being spewed out by the Sun (covered in the centre), and planet Mercury is visible to the left.
The comet’s nucleus is clearly visible, surrounded by a dusty coma and trailing an impressively long tail. SOHO sees the large dust tail edge-on, curving in on itself as it is pushed outward by solar wind.
At the end of the video you can also see a rare phenomenon known as an ‘anti-tail’: a long, thin line that points towards the Sun. This tail is an optical illusion coming from SOHO getting an edge-on view of the larger cometary dust particles that accumulate in the comet’s orbital plane.
Comet C/2023 A3 was seen for the first time early last year. It most likely came from the distant Oort cloud, and the last time this comet flew through the inner Solar System (if ever) was at least 80 000 years ago.
The comet reached an estimated peak brightness just beyond –4 magnitude. (The more negative the visual magnitude value, the brighter the object.) Of the more than 5000 comets SOHO has seen flying past the Sun, only Comet C/2006 P1 (McNaught) was brighter, with a visual magnitude of –5.5.
SOHO’s location between the Sun and Earth gave it a front-row seat, but the same comet has been visible from Earth every evening since 12 October 2024. Throughout October, as the comet moves farther away from the Sun, it will gradually grow fainter and rise higher up in the western sky.
The week that SOHO watched Comet Tsuchinshan–ATLAS was also a wild one in terms of space weather. The Sun unleashed no less than 4 X-class flares (the highest intensity type of flare), 28 medium-intensity M-class flares, and 31 coronal mass ejections – the latter being visible as white clouds of material in the video. All this activity led to two geomagnetic storms on Earth, resulting in beautiful auroras lighting up the night sky.
SOHO, short for Solar and Heliospheric Observatory, is a joint ESA-NASA mission to study the Sun. For almost 29 years now, it has been watching the Sun itself as well as the much fainter light coming from the Sun’s outer atmosphere, called the solar corona. The data shown in this video were taken by the LASCO C3 coronagraph instrument.
Special thanks to Simeon Schmauß, who processed the raw data to create this impressive video. For comparison, here is a video of the comet with more standard data processing – the comet is so bright that it partially saturated SOHO’s sensor.
What types of comets are there?
How are comets named?
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By NASA
NASA/Matthew Dominick NASA astronaut Matthew Dominick captured this timelapse photo of Comet C/2023 A3 (Tsuchinshan-ATLAS) International Space Station as it orbited 272 miles above the South Pacific Ocean southeast of New Zealand just before sunrise on Sept. 28, 2024. At the time, the comet was about 44 million miles away from Earth.
Though the comet is very old, it was just discovered in 2023, when it approached the inner solar system on its highly elliptical orbit for the first time in documented human history. Beginning in mid-October 2024, Comet C/2023 A3 (Tsuchinshan-ATLAS) will become visible low in the west following sunset. If the comet’s tail is well-illuminated by sunlight, it could be visible to the unaided eye. Oct. 14-24 is the best time to observe, using binoculars or a small telescope.
The comet hails from the Oort Cloud, which scientists think is a giant spherical shell surrounding our solar system. It is like a big, thick-walled bubble made of icy pieces of space debris the sizes of mountains and sometimes larger. The Oort Cloud lies far beyond Pluto and the most distant edges of the Kuiper Belt and may contain billions, or even trillions, of objects.
Image Credit: NASA/Matthew Dominick
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