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Breaking: WISE mission misleads public with confusing comet stats

In my day work I am no stranger to government bureaucracies and “programs” manipulating information about their activities until it suits them to do otherwise.  The WISE mission is no different.

In March of this year David Shiga wrote an obviously informed article revealing early results of the WISE mission (below).  Six weeks into WISE’s work, someone revealed to Shiga (I don’t think it is press release material, but prove me wrong) that 16 NEO’s had been identified, and strangely, these objects were in comet-like inclined orbits (making them comets).  Then, this week, six month later, we get an update from the JPL mission team reporting a total of 15 new “comets” have been found, and 25,000 new “asteroids.”

What happened to the original 16 objects with inclined orbits?  Are they now just lumped in with asteroids?  How many of the “asteroids” orbits are inclined (making them comets)?.

The WISE mission is massaging, or least showing no consistency, in their use of the terms comet and asteroid in their press releases or private communication with the media.  I am sure the public will be able to sort this out in six more months as promised in the JPL press release.  But the opaque and clumsy treatment of this important quasi-public information in the popular press in the meantime is disappointing.

I would love for a reader or two to provide insight and clarification regarding these matters.  I do not, for instance, monitor or quite understand the Minor Planet Center. Perhaps all this info is being fed to “Harvard” and WISE feels no responsibility to elaborate in a press releases regarding the finer points of astronomical nomenclature.  Or, maybe you sense the same manipulation-without-explanation  I do…

Besides all those asteroids, WISE has also sighted 15 new comets. It has spied hundreds of potential brown dwarfs — stellar objects that are bigger than a planet but much smaller than a star — and confirmed the existence of 20 of them, including some of the coldest ever known.

Alicia Chang, Associated Press, July 16, 2010

In its first six weeks of observations, it has discovered 16 previously unknown asteroids with orbits close to Earth’s. Of these, 55 per cent reflect less than one-tenth of the sunlight that falls on them, which makes them difficult to spot with visible-light telescopes. One of these objects is as dark as fresh asphalt, reflecting less than 5 per cent of the light it receives.

Many of these dark asteroids have orbits that are steeply tilted relative to the plane in which all the planets and most asteroids orbit. This means telescopes surveying for asteroids may be missing many other objects with tilted orbits, because they spend most of their time looking in this plane.

David Shiga, March 5, 2010, New Scientist

So far, WISE has observed more than 100,000 asteroids, both known and previously unseen. Most of these space rocks are in the main belt between Mars and Jupiter. However, some are near-Earth objects, asteroids and comets with orbits that pass relatively close to Earth. WISE has discovered more than 90 of these new near-Earth objects. The infrared telescope is also good at spotting comets that orbit far from Earth and has discovered more than a dozen of these so far.

JPL press release summarizing WISE findings so far, July 16, 2010

Dark, dangerous asteroids found lurking near Earth

David Shiga, March 5, 2010, New Scientist

An infrared space telescope has spotted several very dark asteroids that have been lurking unseen near Earth’s orbit. Their obscurity and tilted orbits have kept them hidden from surveys designed to detect things that might hit our planet.

Called the Wide-Field Infrared Survey Explorer (WISE), the new NASA telescopelaunched on 14 December on a mission to map the entire sky at infrared wavelengths. It began its survey in mid-January.

In its first six weeks of observations, it has discovered 16 previously unknown asteroids with orbits close to Earth’s. Of these, 55 per cent reflect less than one-tenth of the sunlight that falls on them, which makes them difficult to spot with visible-light telescopes. One of these objects is as dark as fresh asphalt, reflecting less than 5 per cent of the light it receives.

Many of these dark asteroids have orbits that are steeply tilted relative to the plane in which all the planets and most asteroids orbit. This means telescopes surveying for asteroids may be missing many other objects with tilted orbits, because they spend most of their time looking in this plane.

Fortunately, the new objects are bright in infrared radiation, because they absorb a lot of sunlight and heat up. This makes them relatively easy for WISE to spot.


“It’s really good at finding the darkest asteroids and comets,” said mission team member Amy Mainzer of NASA’s Jet Propulsion Laboratory in Pasadena, California, at the Lunar and Planetary Science Conference in Houston, Texas, on Thursday.

WISE is expected to discover as many as 200 near-Earth objects – but astronomers estimate that the number of unknown objects with masses great enough to cause ground damage in an impact runs into the tens of thousands.

Richard Binzel of the Massachusetts Institute of Technology says the dark asteroids may be former comets that have long since had all the ice vaporised from their exteriors, leaving them with inactive surfaces that no longer shed dust to produce tails. He points out that many comets have very tilted orbits, and comets visited by spacecraft have been observed to have very dark surfaces.

20 Responses

  1. My intuitive sense of what highly inclined meteoroids/comets is that they have only one moment and location of crossing Earth’s orbital plane per revolution, and that if this crossing point is not IN the Earth’s orbit, they cannot be a threat to Earth. It would seem logical that this crossing point would more or less be synonymous with the body’s perihelion.

    We know that very few comets (if any?) have a perihelion at 93 million miles from the Sun. If they were, they would certainly be short-period comets and we would be quite familiar with them.

    The Perseids’ radiant is higher in the sky. I can’t yet find anything specific, but the fact that they hit the Earth’s atmosphere shows they are in the plane of the Earth’s orbit, even if they are a bit to the “north” as they pass the Earth’s orbit.

    I would posit that the high-orbit bodies cannot be short period enough to have a perihelion at the Earth orbits. And if not, they cannot be a danger to Earth.

    To be a long(er)-period comet, a body must be somewhat of a Sun-grazer. The perihelion must be well within the Earth’s orbit. This means that if it is also a high-orbit comet, its intersection of the plane of the Earth’s orbit is a single point, at its perihelion. The minimum distance from this crossing point to Earth must be the difference between its perihelion distance and 93 million miles.

    And how about meteoroids? The annual meteor showers should give a glimpse of this. The Taurids and the Leonids are short-period meteor showers that appear to come out of the constellations Taurus and Leo, respectively, and both those constellations are basically “on” the ecliptic, meaning that these showers are in the plane of the planets. Delta Aquariids come out of Aquarius, also on the ecliptic. The Geminids come out of Gemini. (All the zodiacal constellations are along the ecliptic, which is their tie to astrology – they are essentially 12 more-or-less equal segments around the ecliptic.) Those are the ones close to the ecliptic. How about high-orbit ones?

    See: Earth, Moon, and Planets Volume 102, Numbers 1-4 :The Dynamics of Low-Perihelion Meteoroid Streams by Paul A. Wiegert

    The Canadian Meteor Orbit Radar (CMOR) has collected information on a number of weak meteor showers that have not been well characterized in the literature. A subsample of these showers (1) do not show a strong orbital resemblance to any known comets or asteroids, (2) have highly inclined orbits, (3) are at low perihelion distances (<< 1 AU) and (4) are at small semimajor axes (<2 AU). Though one might conclude that the absence of a parent object could be the result of its disruption, it is unclear how this relatively inaccessible (dynamically speaking) region of phase space might have been populated by parents in the first place. It will be shown that the Kozai secular resonance and/or Poynting–Robertson drag can modify meteor stream orbits rapidly (on time scales comparable to a precession cycle) and may be responsible for placing some of these streams into their current locations. These same effects are also argued to act on these streams so as to contribute to the high-ecliptic latitude north and south toroidal sporadic meteor sources. There remain some differences between the simple model results presented here and observations, but there may be no need to invoke a substantial population of high-inclination parents for the observed high-inclination meteoroid streams with small perihelion distances.

    This would seem to support my contention that perihelion would be at << 1 AU. I find it informative that they do not seem to have any good working hypotheses as to how highly-inclined objects GOT highly inclined. I am tentative fan of the "exploding planet" idea, and the more I hear about the more I like it. Occam's Razor and all that rot, in spite of Lyell and uniformitarianism. It is my postion that when current ideas are inadequate it is very bad form to patch together MS-Windows-like failing-all-the-time-when-anything-new-comes-along gobbledegook from current paradigms. Certainly the currently observed processes must be tried first. But when they are inadequate??? For so rudimentary a phenomena, one would think the great minds of the last 400 years would have come up with something by now.

    But the point is them crossing the Earth's orbital plane and what are the chances Earth will be struck.

    All I see says there is essentially no risk whatsoever. Earth is hit by debris all the time – but it is "stuff" in the ecliptic. Looking high and low may seem like some to be a worthwhile endeavor. I think it was probably a waste of money and effort. Even if a high-orbit object DOES come down exactly IN Earth's orbit in ONE journey around the Sun, the chances it will do so at the moment the Earth is there is only passing that spot for 7 minutes a year – only 0.001355% of a year. I mocked probability in a comment elsewhere here, so you can laugh when I say that the odds of us getting hit (barring deflection from Earth's gravitation) are 1 in over 73,000. And that is IF its perihelion = 1 AU. Which it isn't going to be. If it was, we'd see it quite often – and it would have hit at some time in the last 150,000 years, certainly in the last few million. Earth would have swept it out of the sky already, long ago.

    Sorry guys. I don't see any danger. Show me I am wrong, and I will get on board.

  2. Probably the confusion arises from the fact that just because a body is in a comet like orbit, it is not classified as a comet. In order to be officially classified as a comet, it must be observed to be “out-gassing” or have a detectable tail. This is why Chiron is classified both as a comet and an asteroid, since after its discovery it was classified as an asteroid (2060 Chiron), and much later after evidence of it out-gassing (cometary behaviour), as a comet (95P/Chiron).

    having such low albedo, and comet like orbits (high inclinations), suggests that they are extinct or dormant comets, but until cometary activity is observed, they cannot be officially be called comets.

    So there is a consistency in the WISE use of terms of comet and asteroid, since comet like orbit just implies simply that: It is an object that has an orbit that one would expect from comets, but likely no out-gassing or cometary activity has been seen, thus they are classified as asteroids, or NEOs.

  3. Hi Jonny –

    It looks to me like NASA has never heard of “dead comet fragments”. I hope someone tells them before 2022.

    I have my own definition of “out-gassing”, and this press release was a fine example of it.

  4. Regardless as to whether they are dead comet fragments or not, it is the astronomical convention to classify objects upon discovery, as asteroids or comets based upon whether they have a coma or not, i.e. whether they have cometary activity.

    So yes they have heard of dead comet fragments, but on account of them being dead, and not exhibiting cometary activity, then upon discovery, they will be classified as asteroids.


  5. Well then perhaps astronomical convention should adapt to modern knowledge because we now know that these objects come in a wide variety of compositions and perturbed orbits (changing dramatically and often) with a variety of surface crusts that can be ruptured by impacts creating out gassing and outbursts almost randomly. A dead comet implies that it is so depleted of volatiles that not even an impact would cause it to flare into activity. You are vastly oversimplifying the phenomena and then appealing to authority. We know how that worked out with Pluto.

  6. Hi Thomas, appreciatively so, but the point I am making is this. When you look through a telescope, or whatever imaging apparatus you are using, then you see a point of light in a particular orbit. Based solely on this observation, one can only classify the body as an asteroid or comet based upon whether it is exhibiting cometary activity at the time, regardless as to whether it has a comet like orbit or not. So if you observe it to have a coma or tail, then it will be classified a comet, if it has no coma or tail, it is an asteroid. This was the point I was making with the WISE article, and why there seemed to be confusion.

    Further observations though may well reveal their true nature as a comet, and hence be reclassified as such. What we are talking about here is purely the classification system, which is not oversimplification. This is how upon discovery a new body is classified. Take for example 2003 EH1. This is an asteroid designation, and was thought to have been an asteroid until it was dynamically linked with the Quantrantid meteor stream, whose meteors have mean densities that indicative of cometary origin. It also appears to have the typical low albedo surface, as well as a comet like orbit within the 2:1 mean resonance of Jupiter, and Tisserand parameter of 2.064, putting it into a Jupiter family comet orbit. In comparison, Comet Encke’s Tisserand parameter is 3.027, which is in the asteroid region. Many Astronomers do believe that 2003 EH1 is a dormant or extinct comet, and indeed in his book “Meteor Showers and their Parent Comets”, Peter Jenniskens refers to it as such, even though it is not officially classified as one.

    Ultimately, there is nothing in a name, as a small asteroid, or small chunk of comet are equally as devastating upon impact with earth.

  7. What we are talking about here is purely the classification system, which is not oversimplification.

    Which completely neglects modern theories of what we know about the origin and evolution of these materials, and indeed all modern experimental results of what we can observe and measure directly on the samples we have in hand.

    Some of us are a little more sophisticated than those who would only invoke remote observation of distant bodies.

  8. Hi Thomas,

    I still dont think I am making the point clear. So I shall try another time. Yes we have data that shows that some asteroids are cometary in nature, which blurs the lines between what is asteroid and what is a comet. Indeed, we have evidence that defunct comets can look asteroidal in appearance.

    BUT the point of my original post was merely to explain the numbers in the WISE post did not add up, in that it was stated that 16 objects had comet like orbits, and then later it stated that it had discovered 15 comets. I thus pointed out that this apparent discrepancy arises due to the classification system, namely that cometary orbits, or darkened surfaces do not get classified as actual comets, even though they are likely to be defunct or dormant comets. Given that these were preliminary results from WISE, and hence only remotely observed, they could only classify them as either comets or asteroids based solely upon whether they had comae and tails or not.

    Only upon further observation, and scrutiny can astronomers then determine whether these non-comae objects have a cometary origin. There is no neglecting the modern theories etc, by this classification system. It is merely the beginning in the research into a particular newly discovered object. As I have said before, objects can be classified as an asteroid, only later, after further observation be reclassified as a comet, Chiron probably being the most famous aspect.

    Just because it has been classified as an asteroid (which merely puts it into a specific subsection of an astronomical catalogue of objects), will not change the nature of the actual object itself. Thus the classification system of newly discovered objects is simple, but it is not over-simplified.


  9. Jonny, TLE –

    Apparently the nomenclature was developed given the limits of the observation equipment on hand at the time. Just as “Pluto” was declared a planet because other “plutoids” could not be seen. (I know full well that “plutoid” is not an accepted name, but I like it.)

    That said, I’m certain that in this case the name does matter, and matters a lot. The bottom line questions are what hits the Earth, where they come from, and what are their properties. That in turn determines the optimal search strategy, the necessary tools, and the funding necessary for them.

  10. Actually plutoids is the accepted classification now, plutons was fielded for a while but that didn’t last long. I actually blogged in favor of plutoids over plutons on an earlier version of the blob, so of course, I like to delusionally think that my advocacy was the critical tipping point in the pluton/plutoid nomenclature controversy.

    Jonny’s arguments are juvenile, so I’m giving up on it. Just because a body isn’t visibly outgassing when it is discovered is totally irrelevant to the discussion of the evolutionary history, composition and structure of an object, whose orbit is often dramatically perturbed, and whose origin may have been far from its current position.

  11. Then in that case all astronomers are juvenile. I direct you to page 140 of “Meteor Showers and their Parent Comets” by Peter Jenniskens which states

    “In order to obtain a comet designation, it is required that a cloud of dust or gas is detected. That means detecting a fuzziness in the image or other proof that a stream of cometary meteoroids is caused by the minor body”

    The former case is used upon initial discovery of a minor object, the latter case upon further examination of the object such as dynamical modelling. A current case in point is 2003 EH1, which has an asteroidal designation, but is has been shown to maybe have dynamical links with comet C/1490 Y1, is likely the source of the Quadrantid meteor shower (which has grain densities a kin to that of cometary grains, and has a Jupiter family Tisserand invariant. While this is all strong evidence it is not yet “proof” that the body in question is a comet. For example it has not been uniquely proven that it is the the source of the Quadrantidis, since it has also been possible to link comet 96P/1986 (Machholz 1) to the stream (see B McIntosh “Comet P/Machhholz and the Quadrantid meteor stream” Icarus 86, (1990) 299-304). Given that through a telescope 2003 EH1 looks asteroidal, until it has been definitively shown to be be the source of the Quadrantids, or it suddenly out-gasses, it will keep its asteroidal designation.

  12. Then in that case all astronomers are juvenile.

    No, just IAU astronomers obsessed with insanely simple classification nomenclature. Pluto comes to mind.

    While this is all strong evidence it is not yet “proof” that the body in question is a comet.

    Science doesn’t prove things, mathematics does. You seriously need to quit. Stop. Go back.

    As if I care if a remote object is classified a comet or an asteroid. Too funny.

  13. Hi Jonny-

    May I humbly suggest that the IAU MPC use that evidence to define “dead comet” and “dead comet fragment”.

    This would clear things up rather than obfuscate the differences between comets and asteroids.

    I always use the term “piece of stuff from space”, rather than “piece of s**t from space”, when describing impactors, but I doubt if the IAU MPC would adopt the later terminology.

  14. Hi Thomas,

    I think I will quit now, as I have made the point, and you are entitled to your own opinions on the matter. However, it is rather disheartening to encounter the vitriolic responses here, suggesting that I am juvenile for example. It really does soil the atmosphere of this excellent site of George’s.

    As a personal note, I am well aware that science cannot prove things “hence the quotation marks around “proof”. I was never arguing that the composition of a body is unimportant, and indeed it is a very interesting aspect of solar system science, merely explaining the discrepancy of the information in the original article.

  15. Hi Jonny, TLE –

    I have given this matter more thought, and I don’t think my friends in the meteorite community would appreciate the terminology “piece of s**t” from space. On the other hand…

    As the site “S**t That Siri Says Shows”, the internet is not governed by FCC rules. The late Richard Norton kind of owns “Rocks From Space”, leaving the Sh*tfromSpace domain name open.

    Sub pages could have images of large asteroids and comets headed our way (Big Pieces of S**t from space), meteorites (Little Pieces of S**t from space), and craters (Holes left by Big Pieces of S**t from space).

    Then there could be another page, “S**ty Theories about “S**t from space”.

    The reason for this last topic is that by your definition the smaller fragments of COMET SW9 can not be seen, little less be seen outgassing. We know they are still there by the law of the conservation of mass, and we know they are headed our way, arrival in our neighborhood in 2022.

    If I agree to call those comet fragments “asteroids”, could I get all of the Hubble observation time until I can locate them exactly?
    They do fall under the definition of NASA’s responsibility in the George Brown Jr amendment.

  16. Indeed, there is a tremendous amount of stuff out there but most of it is just stuff, far away. It’s the stuff that crosses near the orbit of Earth that concerns me, and then the only label I’m really interested in right now is ‘found’. Unfound stuff is problematic and I predict soon more found unfound stuff will also become problematic.

    Our ignorance of unfound stuff is profound, other than we know it’s out there and we have fair to poor knowledge of what it’s made of, and where it is exactly. That’s what finding is all about. I can’t wait for future visiting.

    That’s kind of what all this is about. So can we now return to the credibility problem of the YD impact? Thanks.

    Anyways, surely active outgassing comets and cometary fragments are capable of impacting the Earth.

    Dead dessicated comets could hit it too. So can rocks and dirt and stuff.

    Some of it is relatively pure nickel and iron.

    Again, it’s when, where and what.

  17. TLE –

    The exchange with Jonny was fun, but its over. As George put it,”In my day work I am no stranger to government bureaucracies and “programs” manipulating information about their activities until it suits them to do otherwise. The WISE mission is no different.” In other words, he deals with government BS everyday.

    I never left the Holocene Start Impacts. It is likely that more than one piece hit. The problem now is to locate craters from some of the bigger pieces. Theoretically, if we just generally sample the layer of impactites (let’s call it the Usselo Horizon, and not the Black Mat) then local densities may lead us to some craters.

    There are other structures already identified that have to be dated yet.

    Its kind of like looking for the NEO detection budget in the NASA budget. You see some key words, then try to find some other key words, and then finally you’ll see a line item.

  18. Hi George –

    The only instrument that we now have which can image comet 73P’s debris stream (Schwassmann-Wachmann 3’s) is Hubble. This debris stream is headed our way in 2022. At 7,000,000,000 people, a hiccup in climate will lead to starvation for many. Also, these are comet fragments, and outgassing will change their orbits.

    Any guess what we do not have?

    Imagery of this debris stream from Hubble.

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