Comet Whacked Neptune 200 Years Ago

Neptune. Credit: NASA

Researchers studying Neptune’s atmosphere found evidence that a comet may have hit the planet about two centuries ago. Was this a “cold-case” file re-opened, or did they discover a way to travel back in time to witness a long-ago event? To make the discovery, a team from the Max Planck Institute for Solar System Research actually used the Herschel Space Telescope’s PACS (Photodetector Array Camera and Spectrometer) instrument, along with what was learned from observations from when the Shoemaker-Levy 9 hit Jupiter sixteen years ago.

The 1994 impact on Jupiter was watched and documented by Voyager 2, Galileo and Ulysses, and today this data helps scientists detect cometary impacts that happened many, many years ago. In fact, just in February of this year, scientists from Max Planck discovered strong evidence for a comet impact on Saturn about 230 years ago. These “dirty snowballs” leave traces of water, carbon dioxide, carbon monoxide, hydrocyanic acid, and carbon sulfide in the atmosphere of the gas giant planets. These molecules can be detected in the radiation the planet radiates into space.

So, the team turned their attention to Neptune, and used the PACS to analyze the long-wave infrared radiation of Neptune.

The atmosphere of Neptune mainly consists of hydrogen and helium with traces of water, carbon dioxide and carbon monoxide. However, the scientists detected an unusual distribution of carbon monoxide in the stratosphere, the upper layer of the atmosphere, and found a higher concentration than in the layer beneath, the troposphere. “The higher concentration of carbon monoxide in the stratosphere can only be explained by an external origin,” said MPS-scientist Paul Hartogh, principal investigator of the Herschel science program. “Normally, the concentrations of carbon monoxide in troposphere and stratosphere should be the same or decrease with increasing height,” he said.

Another theory suggested that a constant flux of tiny dust particles from space introduces carbon monoxide into Neptune’s atmosphere. However, the newest observations from PACS does not lend credence to that idea, and the team concluded the only explanation for these results is a cometary impact. Such a collision forces the comet to fall apart while the carbon monoxide trapped in the comet’s ice is released and over the years distributed throughout the stratosphere.

“From the distribution of carbon monoxide we can therefore derive the approximate time, when the impact took place,” said Thibault Cavalié from MPS, which showed the impact was about 200 years ago.
PACS was developed at the Max Planck Institute for Extraterrestrial Physics, and it analyzes the long-wave infrared radiation, also known as heat radiation, that the cold bodies in space such as Neptune emit.

Source: Max Planck

21 Replies to “Comet Whacked Neptune 200 Years Ago”

  1. Something whacked this way comes.

    Hooray for thermodynamical imbalances!

  2. Navneeth, that is cute!

    Wonder if Plancklets believe in Heisenberg or Schroedinger, and if so if they keep a Planck Mass?

  3. Hmm… a comet hits Saturn +/-230 years ago, then another hits Neptune +/-200 years ago. Given the approximate dates, I wonder if this is more than simply coincidence? The planetary alignment that allowed the Voyager missions to reach the outer planets occurs every 176 years and happened in the late 1970’s. Those alignments may also disturb the orbits of cometary objects in the Kuiper belt and/or the Oort Cloud. Given long transit times of cometary bodies from those two sources, I wonder if this could this be part of a suspect ‘coincidence’?

  4. If Neptune is mostly Gaseous, how exactly does a Comet “Wack it? ..just curious…

  5. I wonder if this is more than simply coincidence?

    I had the same thought, but made the opposite hypothesis: that there’s a hitherto un-modelled atmospheric process that mimics a two hundred year cometary signature in the upper atmosphere.

    Easy enough to test: (1): look at Uranus; (2) track Neptune and Saturn over time: if you get slow decay with new peaks, it’s comets, if not, it’s something else.

    It’s my version of Occam’s Razor: given two explanations, the more boring one is true. Applies only to press releases, not actua;l scientific papers.

  6. It impacts it just as Shoemaker-Levy 9 hit Jupiter in 1994. The comet generates an enormous shock wave as it enters increasingly dense gas.

    You don’t hear a lot about Neptune. At UT Mars has 833 pages and Neptune has 16. Though Neptune muscles out Uranus with only 5. It’s cold an lonely out there, and astronomically these frigid small gas giants get the Rodney Dangerfield award of “no respect.”


  7. @LC:
    lol, I understand thanks.

    It’s too bad we don’t hear more about these two worlds. I think modern Cassini type probes for Uranus and Neptune and their various icy moons should be one of NASA’s top priorities going forward.

  8. Bjorn, they believe in Heisenberg and Schroedinger simultaneously, but they avoid observing Planck mass because one of them would become real and the other one would disappear.

  9. -Aqua

    No. The planetary alignment could not have affected the oort cloud. If the as-yet-undetected oort cloud was affected by planetary alignments, we would have gotten a shower of comets in the seventies. Also, the Saturn impact would be before the planetary alignment (assuming the method is accurate).

  10. @Tauridborn: +/-230 years… 2010 – 1980 = 30 + 176 = 206 years. Still… you are right, the Oort Cloud is at approx. 2,000 – 50,000 AU. Any influence from our solar systems gas giants would have to had have been caused by a much higher resonance period to have had any effect – not 176 years, but 352 or 528 or even 704 years? Hmmm… oTay… Kuiper belt objects then?

    Sedna is thought to lie in the Oort Cloud.

    From Wikipedia: “only four currently known trans-Neptunian objects—90377 Sedna, 2000 CR105, 2006 SQ372 and 2008 KV42—are considered possible members of the inner Oort cloud.”

    “..we would have gotten a shower of comets in the seventies…” And not just any old comet(s) either, like Comet West, or Comet Kohotek or Comet Bennett…

  11. The grand alignment in the late 70’s could NOT have been an influence on comets sighted in that time frame… unless due to a previous grand alignment.

  12. Aqua…
    there are more comets than we know about, so any impact was likely a coincidence. Look how many odd ball comets we watch (through SOHO) impacting our star.

    Personally, I like “Plancketeers”. Perhaps you will start something.

    Now we know the ice-giants aren’t as boring as we once thought, it would be nice to send something out there to learn more. Unfortunately, NASA first and foremost must come up with projects which interests those who control the purse. Right now, this seems to lean towards finding life, or finding something which will tell us where “we” came from. Along with a couple of other projects which don’t need to be said.

  13. Nancy, was it the “The Simpsons” or “The Sopranos” that inspired the verb in your headline? Me, I prefer this verb:

    Am I just getting old and cranky? I really was in a good mood when I logged on tonight…anyway, nice article and minna-san, be nice to humans and snakes.

  14. While a Modern Plankinator would have studied Heisenberg and Schroedinger, she also knows her Everett, DeWitt, Tagmark, et al. And the in words of that sexy British gentleman in that nice but cancelled TV show, “if I could only solve this damn decoherence equation”….

    Copenhagen ain’t the only game in town!

  15. Indeed, Copenhagen is near the only game _not_ in town, since decoherence was shown to be non-instantaneous (and even gradual). It is a useful toy model now, but the actual physics is predicted by many worlds (for one).

  16. I don’t know how quantum mechanics got into this thread. The problem with many worlds is that it is an interpretation of quantum mechanics meant to reduce a physics which involves complex numbers and spinors into something we can understand in our standard sense of things. This is the case with all interpretations, from Copenhagen to Bohm’s idea of some interior classical-like particle and so forth. They are all in a sense workable, or solve certain types of problems. Yet there is no decision process which allows us to conclude one ir correct of all others.

    The outer gas giant planets are in some ways ignored a bit. However, as our knowledge of what might be called space geography increases the amount of territory we have not explored increases. I call this space geography, or it might in some cases be called geology, for once spacecraft probe planets the scientific focus changes in some ways from astronomy. In order to cover the geography of the solar system in some extensive way is a daunting challenge. Further, space dollars do not gush forth exactly.


  17. I was not aware that Voyager 2 documented SL9’s impact on Jupiter.

    Anyone have any info on what V2 was able to see and document on Jupiter from so far away?

  18. @RUF

    Voyager 2 observed Jupiter with a UV spectrometer and radiowave experiments for over a month at the time of the impacts (no optical imaging was attempted). The results were null. According to a 1994 JPL release:

    “The Voyager 2 spacecraft used two of its scientific
    instruments to look at the impacts of Comet Shoemaker-Levy 9
    fragments as they impacted Jupiter July 16-22. Both the
    ultraviolet spectrometer and the planetary radio astronomy
    experiments were used in the observations. Neither instrument
    detected any UV emission or radio signals during the impacts.
    The spacecraft began its observations of Jupiter on July 8 and
    will continue to observe the planet until August 17. At the
    time of the comet impacts, Voyager 2 was 6.1 billion kilometers
    (3.7 billion miles) from Jupiter.”

  19. It is amazing that Voyager 2 was used to make these observations given its considerable distance from Jupiter.


  20. Yeah I agree LC, WOW.

    Voyager continues to be my favorite NASA mission EVER. Moon landings included.

Comments are closed.