Category Archives: Comet 67P/Churyumov-Gerasimenko

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The Rosetta Mission at Comet 67P Will Soon End

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Studying a Comet Long Term

This four-image montage shows the spectacular region of activity at the 'neck' of 67P/C-G. This is the product of ices sublimating and gases escaping from inside the comet, carrying streams of dust out into space. ESA/Rosetta/NAVCAM
This four-image montage shows the spectacular region of activity at the ‘neck’ of 67P/C-G. This is the product of ices sublimating and gases escaping from inside the comet, carrying streams of dust out into space. ESA/Rosetta/NAVCAM

I’ve been a comet fan since my grad school days. That was when I got pointed at Comet Halley and told, “study these images, and let’s figure out what’s happening with the plasma tail”. So, I pored over images of the comet taken from 1985-1986. I made lots of measurements and worked on papers with my team members. Eventually, we figured out what was happening with the plasma tail (hint: it’s affected by the solar wind). It was a pretty exciting time in my life, standing at the “frontier” of comet science (at that time) and opening my mind to the idea that what happens in the solar wind can make intricate “designs” in the shape and behavior of a plasma tail.

During that whole time, I was also intrigued by what a comet REALLY looks like. We didn’t have any close-up pictures of a comet nucleus. Sure, we had the Fred Whipple model of a chunky block of dusty ice (or icy dust, if you prefer) to study. And, there WERE some Giotto spacecraft images of the Halley nucleus. But they had to suffice until we could get REAL close-ups. What was needed was a long-term study of a nucleus. That’s what the Rosetta mission has done at the nucleus of Comet 67P/Churyumov-Gerasimenko.

Rosetta Orbits a Piece of Solar System History

For the better part of two years, the Rosetta spacecraft has visited the comet. It studied the chemical composition, sent back images, and gave astronomers the longest “timelapse” look at a comet ever. Along with its Philae lander, which functioned for only a short time, Rosetta is a great achievement. It’s something the European Space Agency and scientists around the world can be very proud to have sent. They’ve orbited a major piece of solar system history. They opened a window into the distant past when comets formed from materials that existed before the Sun and planets did. Studying a comet is like opening a treasure box.

In a few weeks, the mission will send its final images and data, and on September 30, 2016, the orbiter will do a slow crash landing on the surface of the comet. Its last messages should contain some very high-resolution images and data. You can follow the Rosetta mission at the ESA Website for the mission and track the spacecraft’s final days and weeks.

Rosetta: the Executive Summary

It’s been an amazing couple of years. Sure, we see what the comet’s surface looks like with its icy plains, boulders, and rocky inclusions. However, Rosetta’s chemical analysis on the comet’s ices and dust reveal information about the comet’s origins in the early epochs of the solar system’s formation. It also shows that the comet contains ingredients crucial to the formation of life. Mind you, Rosetta didn’t find life. However, uncovering the ingredients of life tells an important story. What did it find? Rosetta detected the amino acid glycine as well as the element phosphorus in the comet’s ices. These are key elements in our DNA and cell structures.

Comets as a Source of Water?

Another question astronomers wanted to answer was “Did Earth’s water come from comets?” Rosetta showed that the comet’s water chemistry is slightly different from Earth’s water. That means that ocean water on our planet didn’t all come from comets like 67P. Understanding where Earth’s water came from is still a big question in planetary science, and now astronomers are looking at other comets and asteroids for keys to the mystery.

I’m looking forward to the last images and data from Rosetta. I’m sure many comet fans, scientists, and graduate students are, too. There’s enough work in the treasury of information the spacecraft sent back to keep whole teams busy for years. In the end, even though Rosetta will no longer be working, its work WILL live on. That’s a major legacy for any mission!

Comet 67P/Churyumov-Gerasimenko, rosetta

Scientists Have NOT Discovered Life on Comet 67P

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Speculation Runs Rampant in the Face of Facts

UP close and personal with Comet 67P/Churyumov-Gerasimenko. Courtesy Rosetta/ESA.
UP close and personal with Comet 67P/Churyumov-Gerasimenko. Physical processes are creating these surface features. Courtesy ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

I know it’s very tantalizing to fantasize about life on other worlds, or think about comets and asteroids strewing life-seeds around the planets as they go around the Sun. It’s fuel for hours of fun discussion at cocktail parties, and there’s some serious science going on investigating these possibilities.

But, come on, these stories in the mainstream media, fed by a press release that should have never have escaped from the Royal Astronomical Society reporting on what astrobiologists Max Wallis and Chandra Wickramasinghe speculated about Comet 67P are just plain wrong.

Let me put it plainly. There has been NO life found on Comet 67P/Churyumov-Gerasimenko. None.  Scientists have found all kinds of very cool and amazing surface features, and have been witnessing jets carving up the surface. But, they haven’t found life there, no matter how much a pair of eminent scientists want to speculate differently.

What Does the Team Say?

If the Rosetta team mission scientists had found life — and none of their instruments are built to detect the kind of life being suggested exists there — they’d be talking it up big time right now. But the team can’t and in fact, has come out saying that finding any life on the comet as “highly unlikely.” And that’s as it should be. Extraordinary claims require extraordinary proof, which doesn’t exist. And, these stories are just not doing justice to the actual real science of astrobiology, which also requires the same rigorous proof as other disciplines.

The articles I’ve seen are reporting on the commentary of two scientists who not on the Rosetta mission. These are two people who have been long active in the search for life elsewhere. They made some suggestions that the presence of organics on the comet are evidence of some kind of action by micro-organisms. They have nothing to prove their suggestions, but that hasn’t stopped the press, led by the Guardian, to run wild with a “LIFE FOUND!!!” story. (To be fair, the Guardian has now published a more sensible article.)

Despite what the actual Rosetta mission scientists have said — and you’d think they’d be the most qualified to speak about the comet they’re actually studying, right? — some journalists have just taken the press conference as dictation and published stories conflating”carbon-rich compound” and “organic molecules” with “life”.  Not quite, folks. They’re precursors, but they aren’t life. Something which escaped the notice of the writers of the clickbait stories I’ve seen floating around.

Finding Life Tantalizes Us

Now, since all life is chemical, finding organic compounds (also made up of chemicals) necessary to create life is important. And, there ARE organics on the comet. In fact, they’re all over the solar system, including comets. That makes them quite common. But, carbon-rich organic compounds aren’t living beings, any more than a mixture of water and clay is a living being.

Finding them on Comet 67P is NOT the same as finding life there. It’s like saying, “There’s water on that planet, so there must be life.” Water doesn’t equal life any more than carbon-based dust does. It’s part of the environment that might be hospitable for life, but it’s not life.

What the Comet Actually Shows Us

Active regions in an area called "Seth" on Comet 67P. These semi-circular pits are areas where active jets have been spotted. Courtesy: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Active regions in an area called “Seth” on Comet 67P. These semi-circular pits are areas where active jets have been spotted. Courtesy: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

There are some pretty interesting features on the surface of 67P, but most of them are explained by dust jets, dust deposition, sublimation of ices off the surface, and so on. To claim, without evidence — that microbial life, which hasn’t been found anywhere but Earth (so far) — has anything to do with mini pits, surface etchings, and  boulders on the surface of the planet. Since we know the chemical composition of the comet’s surface, it’s best to go with the explanations that work for that complex mix of gases, ices, and dust.

To be honest, the best possible explanations for the surface features on the comet come from studying the processes at work on the materials already there. Those are processes such as sublimation and solar heating, which leads to jets cutting through the mix of ices and dust that make up the comet. Those processes that act on ices and dust in a vacuum can easily explain what we’re seeing. No need to invoke life, which requires another magnitude of complexity and a lot of other chemistry that hasn’t been detected there.

I really do get tired of these stories from the “mainstream media” that pick up little interview bits with scientists but don’t bother to check the facts or ask the tough questions. The writers who posted the original story (based on a press release) just accepted everything at face value and ran with a wildly screaming “LIFE on a COMET!!!” story.  It sells papers and views on web sites, but it’s click bait journalism and does no one any favors. (Well, it sells ads, but that’s not why we do science, folks.)

The story of Rosetta at Comet 67P is cool already, we don’t need jazzed up headlines falsely implying life on the comet to sell clicks to interest the public.