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New Horizons: Results and Interpretations

Another reminder that the days of the lone scientist making breakthroughs in his or her solitary lab are today counterbalanced by the vast team effort required for many experiments to continue. Thus the armies involved in gravitational wave astronomy, and the demands for big money and large populations of researchers at our particle accelerators. So, too, with space exploration, as the arrival of early results from New Horizons in the journals is making clear.

We now have a paper on our mission to Pluto/Charon and the Kuiper Belt that bears the stamp of more than 200 co-authors, representing 40 institutions. How could it be otherwise if we are to credit the many team members who played a role? As the New Horizons site notes: “[Mission principal investigator Alan] Stern’s paper includes authors from the science, spacecraft, operations, mission design, management and communications teams, as well as collaborators, such as contributing scientist and stereo imaging specialist (and legendary Queen guitarist) Brian May, NASA Planetary Division Director Lori Glaze, NASA Chief Scientist Jim Green, and NASA Associate Administrator for the Science Mission Directorate Thomas Zurbuchen.”

New Horizons still has the capacity to surprise us, or maybe ‘awe’ is the better word. That’s what I felt when I saw the now familiar shape of Ultima Thule highlighted on the May 17 Science cover in an image that shows us what the object would look like to the human eye. The paper presents the first peer-reviewed scientific results and interpretations of Ultima a scant four months after the flyby.

As to the beauty of that cover image, something like this was far from my mind during the 2015 Pluto/Charon flyby, when the occasional talk ran to an extended mission and a new Kuiper Belt target. I wouldn’t have expected anything with this degree of clarity or depth of scientific return from what was at that time only a possible future rendezvous, and one that would not be easy to realize. Another indication of how outstanding New Horizons has been and continues to be.

Image: This composite image of the primordial contact binary Kuiper Belt Object 2014 MU69 (nicknamed Ultima Thule) – featured on the cover of the May 17 issue of the journal Science – was compiled from data obtained by NASA’s New Horizons spacecraft as it flew by the object on Jan. 1, 2019. The image combines enhanced color data (close to what the human eye would see) with detailed high-resolution panchromatic pictures. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute//Roman Tkachenko.

I’d be hard-pressed to come up with a space-themed cover from Science that’s more memorable than that. For that matter, here’s an entertaining thought: What would the most memorable space-themed Science cover of, say, 2075 look like? Or 2250? Let’s hope we’re vigorously exploring regions from the Oort Cloud outward by the latter year.

Meanwhile, New Horizons is helping us look back toward our system’s earliest days.

“We’re looking into the well-preserved remnants of the ancient past,” says Stern. “There is no doubt that the discoveries made about Ultima Thule are going to advance theories of solar system formation.”

Indeed. The two lobes of this 36-kilometer long object include an oddly flat surface (nicknamed ‘Ultima’) and the much rounder ‘Thule,’ the two connected by a ‘neck’ that raises the question of how the KBO originally formed. We seem to be looking at a low velocity merger of two objects that had originally been in rotation. Their merger is important; remember, we’re dealing with an ancient planetesimal. From the paper:

For MU69 ’s two lobes to reach their current, merged spin state, they must have lost angular momentum if they initially formed as co-orbiting bodies. The lack of detected satellites of MU69 may imply ancient angular momentum sink(s) via (i) the ejection of formerly co-orbiting smaller bodies by Ultima and Thule, (ii) gas drag, or both. This suggests that contact binaries may be rare in CCKBO [Cold Classical Kuiper Belt Object] systems with orbiting satellites. Another possibility, however, is that the lobes Ultima and Thule impacted one another multiple times, shedding mass along with angular momentum before making final contact. But the alignment of the principal axes of MU69 ’s two lobes tends to disfavor this hypothesis.

Also interesting is the possibility of tidal locking of the two lobes before their merger:

In contrast, tidal locking could quite plausibly have produced the principal axis alignment we observe, once the co-orbiting bodies were close enough and spin-orbit coupling was most effective… Gas drag could also have played a role in fostering the observed coplanar alignment of the Ultima and Thule lobes… Post-merger impacts may have also somewhat affected the observed, final angular momentum state.

And let’s consider what the science team has to say about Ultima Thule’s color. Like many other objects found in the Kuiper Belt, it’s red, much redder than Pluto. This obviously has significant interest because of what it implies about the organic materials on the surface and how they are being modified by solar radiation. Here the mixture of surface organics differs from other icy objects previously examined, though not all:

There are key color slope similarities between the spectrum of MU69 and those of the KBO (55638) 2002 VE 95 (45) and the escaped KBO 5145 Pholus… Also, these objects all exhibit an absorption band near 2.3 mm, tentatively attributed to methanol (CH3OH) or perhaps more complex organic molecules intermediate in mass between simple molecular ices and tholins… Similar spectral features are also apparent on the large, dark red equatorial region of Pluto informally called Cthulhu… suggesting similarities in the chemical feedstock and processes that could operate there and on MU69.

The paper points out that we see evidence for H2O ice in the form of shallow spectral absorption features, indicating low abundance in the object’s upper surface, as compared with planetary satellites and even some Kuiper Belt objects with clearer H2O detections. As expected, we do not see the spectral signatures of volatile ices such as carbon monoxide, nitrogen, ammonia or methane, which were observed at Pluto. These were not expected at MU69 “…owing to the ready thermally driven escape of such ices from this object over time.”

We’re left with a lot of unanswered questions, including the nature and origin of surface features like ‘Maryland crater,’ the largest (8 kilometer wide) scar on the KBO, likely the result of an impact, and the various bright spots and patches. How much of the pitted surface can be related to outgassing via sublimation, or material falling into already existing underground spaces? Bear in mind that the data return from New Horizons is to continue until late summer of 2020. Meanwhile, the spacecraft continues to measure the brightness of other Kuiper Belt objects while also mapping the charged-particle radiation and dust environment of its surroundings.

The paper is Stern et al., “Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object,” Science Vol. 364, Issue 6441 (17 May 2019). Abstract.


Comments on this entry are closed.

  • ljk May 21, 2019, 8:46

    Paul Gilster said in the main article:

    “What would the most memorable space-themed Science cover of, say, 2075 look like? Or 2250? Let’s hope we’re vigorously exploring regions from the Oort Cloud outward by the latter year.”

    I sincerely hope well before the latter date we will have images and data from the nearest star systems thanks to interstellar vessel missions to them. Also solid evidence for alien life, both intelligent and otherwise.

    • Alex Tolley May 21, 2019, 11:19

      I do too. Let’s just hope that the planet won’t be diverting all its resources to keeping some fraction of the population sheltered and fed in the wake of rising temperatures and coastal flooding with all ideas of space exploration extinguished as the survivors gaze on the dreams of the 20th century.

      • Robert May 21, 2019, 13:33

        It seems to me if you think Climate Change really is that big of an existential threat (as the survivors…) then you should want to stop spending money on these kinds of missions. Personally, I think if the public at large chooses to buy electric vehicles over the next couple of decades that alone would likely solve the climate issue. We can and should fully continue on with all non climate related programs including space related research and development.

        • Alex Tolley May 21, 2019, 20:21

          Electric cars are insufficient to solve global heating. The global economy needs to be decarbonized just to halt continued heating. We would then need to extract CO2 from the air and ocean to get back to where we were prior to the industrial revolution. If we don’t act before the ice sheets melt, then we still lose coastal cities.
          We shouldn’t stop missions. There is more than enough funding if diverted from other expenditure. But if we don’t act, then any discretionary funding may be very small scale in a century or so.

          • Robert May 22, 2019, 13:00

            The electric car industry will bring with it associated energy production and storage technologies which will greatly decarbonize the economy. It’s not just a few electric cars driving around. Cars themselves could amount to a mobile production and storage grid when not in use depending on the specific technologies involved. I think the markets will do all this without heavy handed government intervention or handing over the world economic policy to single minded environmental groups.

            These technologies will help space research and development also.

      • Alex T. May 22, 2019, 2:44

        There is huge probability that climate changes are not related to homo sapience , but periodical and natural events and property of our planet so Earth’s civilization has to accept reality and adopt to it. The things that are not good for human being, may be perfect for other life on the planet.

        • Robert May 22, 2019, 13:09

          There are plenty of reasons to decarbonize aside from Climate Change. According to the U.N., pollution from various fossil fuels alone causes millions of premature deaths a year. Not to mention the dangers and consequences of mining, drilling, processing and transporting fossil fuels.

          To me the issue of limiting if not ending the use of fossil fuels is quite independent of why the climate is changing. We still have to deal with a changing world regardless.

      • Thomas W. Hair May 22, 2019, 12:14

        Can we please stop talking about “big” climate all the time. It’s virtue signalling nonsense, not science. The world isn’t going to end or become Venus for the next few hundred million years. But the base rate fallacy is alive and well in the context of CO2 parts per million. I respect everyone here, but give it a rest. I have lived on a concrete lined sea level canal in south Florida for most of my life and I cannot detect any significant change…and that is not anecdotal evidence. This former city council member knows that the city of Cape Coral keeps the most precise records of sea level on the planet. We have 400 miles of canals. Google Earth Cape Coral, your climate fantasies will be in for a dose of reality.

        • Gary Wilson May 22, 2019, 15:02

          With respect Thomas human induced climate change is real and very dangerous and has been confirmed by thousands upon thousands of peer reviewed studies. We (humans) have increased CO2 levels by 50% above pre-industrial levels. Average global temperatures have increased by 1 C already. The effect is non-linear. Ocean levels have only risen a small amount so far but the future is a far different thing. Sea levels will rise dramatically in the future. All the data you could possibly need is available in the IPCC records. Extreme weather events are increasing in severity and frequency. That data is also available. Insurance companies are very aware of this. This is undeniable science.

          • Robert May 22, 2019, 17:49

            The issue isn’t is warming happening, the issue is how much is human caused. It’s probably not 100%. Yet some people talk about it in apocalyptic. In spite of the rhetoric and tactics that marginalize any scientist with a minority view, and there are some, there is still room for legitimate debate. The issue has been overly politicized and sincere scientists with alternative views are just shouted down which is not the way science is supposed to work.

          • Thomas W. Hair May 22, 2019, 22:39

            Gary, I agree to a degree with your statement. I guess what I disagree with is the group think associated with the topic. The IPCC is not an arbiter of scientific knowledge. It is a political organization with an agenda cloaked around a kernel of seemingly perfect knowledge that we are far from completely understanding at this stage. The full data set is far from in. This planet was inhabitable for humans 600 million years ago. It will be uninhabitable again in less than four hundred millions years. That is 10 percent of the total lifetime this planet will exist. The most powerful force in the universe is not the giant black hole at the center of M87. It is the human will to live another day. We, and our children of the mind, will persevere far into the future regardless. The future is for optimists, and I for one, believe that to believe otherwise is nihilistic in the extreme. The nihilist calls the optimist naive. I shall wear that as a badge of honor.

          • Alex T. May 25, 2019, 2:38

            Science knows also that there was CO2 level changes in the far past, very far from industrial era… We can blame Atlantida civilization or Greek Gods doing such “bad” things with ancient and paleontologic climate changes (including CO2), but most probably it is mother Earth thermal activity… We can only take it as-is…

  • ljk May 21, 2019, 13:48
    • Paul Gilster May 21, 2019, 14:01

      More on this tomorrow, when I look at the paper.

  • Thomas W. Hair May 21, 2019, 16:52

    That simple picture is almost certainly lost on most folks, and that is okay. We all have busy lives and such, but when I stare at that magnificent photo I get a preternatural chill.

  • Geoffrey Hillend May 21, 2019, 17:35

    The volatile ices have escaped MU 69 due to it’s small size, so it has a low escape velocity.

  • Alex Tolley May 21, 2019, 20:27

    I wonder whether those pale circles are the remnants of the necks of other contact points, whether from the same body or others.

    • Bruce D. Mayfield May 22, 2019, 0:06

      Yes, or if not necks then at least the joints between the various chunks that clumped together to form Ultima.

  • ljk May 22, 2019, 10:30


    2019 May 22

    Primordial Contact Binary 2014 MU69

    Image Credit: NASA, Johns Hopkins University APL, Southwest Research Institute, Roman Tkachenko

    Explanation: Primordial contact binary 2014 MU69, also known as Ultima Thule, really is very red. In fact, it’s the reddest outer solar system object ever visited by a spacecraft from Earth. Its reddish hue is believed to be due to organic materials on its surface.

    Ruddy color and tantalizing surface details seen in this composite image are based on data from the New Horizons spacecraft recorded during the January 1 flyby of the farthest world yet explored. Embedded in the smaller lobe Thule (top), the 8 kilometer wide feature nick named Maryland crater is the largest depression known on the surface of Ultima Thule.

    Transmission of data collected from the flyby continues, and will go on until the late summer 2020 as New Horizons speeds deeper into the dim and distant Kuiper Belt.

  • Michael T May 23, 2019, 0:33

    Electric cars are a great thing, as is a good storage system, but we still need to address how the electricity is initially generated. It’s true that better storage systems (e.g., Tesla’s batteries) will enhance the capabilities of renewable but variable energy sources (and help cope with fluctuating demand).

    It is appropriate for government to set emission standards and to encourage uptake of renewables in various ways. Unfortunately some governments, far from being controlled by green groups, are actually *hostile* to renewables, and actively promoting the expansion of fossil fuels in collaboration with private interests (incidentally burning up resources that are valuable for other things such as the chemical industry).

    Private initiatives such as Tesla’s are of course a good thing. We need to work in the private, governmental and personal spheres.

    Let’s keep THIS planet pleasantly blue, brown and green with some cloud :-)