arXiv 1808.02618: Earth and Planetary Astrophysics OSSOS: XIII. Fossilized Resonant Dropouts Imply Neptune's Migration was Grainy and Slow

Paper: OSSOS: XIII. Fossilized Resonant Dropouts Imply Neptune's Migration was Grainy and Slow
Authors: S. M. Lawler, R. E. Pike, N. Kaib, M. Alexandersen, M. T. Bannister, Y.-T. Chen, B. Gladman, S. Gwyn, J. J. Kavelaars, J.-M. Petit, K. Volk

Abstract: The migration of Neptune's resonances through the early Kuiper belt has left signatures of the migration timescale and mode in the distribution of small bodies in the outer Solar System. Here we analyze five published Neptune migration models in detail, focusing on the high pericenter distance (q) trans-Neptunian Objects (TNOs) near Neptune's mean-motion resonances. We focus on the TNOs near the 5:2 and 3:1 resonances, because they have large detected populations, are outside the main classical belt, and are relatively isolated from other strong resonances. We compare the observationally biased output from these dynamical models with the detected TNOs from the Outer Solar System Origins Survey, via its Survey Simulator. All of the four new OSSOS detections of high-q non-resonant TNOs are on the Sunward side of the 5:2 and 3:1 resonances. We show that even after accounting for observation biases, this asymmetric distribution cannot be drawn from a uniform distribution of TNOs at 2-sigma confidence. We find that the dynamical model that uses grainy slow Neptune migration provides the best match to the real TNO orbital data. However, due to extreme observational biases, we have very few high pericenter distance TNO discoveries with which to statistically constrain the models. We show that a deeper survey (to a limiting r-magnitude of 26.0) with a similar survey area to OSSOS could statistically distinguish between these five Neptune migration models. We speculate that the cycle of resonance sticking and Kozai oscillation within a resonance, followed by resonant dropout into this fossilized high-q population, could potentially explain all but the two very highest-q TNOs discovered to date.

My Comment: To me this is so very much the heart of astronomy science. We very rarely can do an experiment in the lab, so we have to do as much as possible with what we are able to observe. Our theories must be realized by careful simulation of what the physics say they do, and then must be carefull compared to well-characterized observations.

My Scrawling Notes:

arXiv:1808.00609 - The excitation of a primordial cold asteroid belt as an outcome of the planetary instability

Paper: The excitation of a primordial cold asteroid belt as an outcome of the planetary instability
Authors: Rogerio Deienno, Andre Izidoro, Alessandro Morbidelli, Rodney S. Gomes, David Nesvorny, Sean N. Raymond

Abstract: The main asteroid belt (MB) is low in mass but dynamically excited. Here we propose a new mechanism to excite the MB during the giant planet ('Nice model') instability, which is expected to have featured repeated close encounters between Jupiter and one or more ice giants ('Jumping Jupiter' -- JJ). We show that, when Jupiter temporarily reaches a high enough level of excitation, both in eccentricity and inclination it induces strong forced vectors of eccentricity and inclination across the MB region. Because during the JJ instability Jupiter's orbit `jumps' around, the forced vectors keep changing both in magnitude and phase throughout the whole MB region. The entire cold primordial MB is thus excited as a natural outcome of the JJ instability. The level of such an excitation, however, is typically larger than the current orbital excitation observed in the MB. We show that the subsequent evolution of the Solar System is capable of reshaping the resultant over-excited MB to its present day orbital state, and that a strong mass depletion (∼90%) is associated to the JJ instability phase and its subsequent evolution throughout the age of the Solar System

My Comment: Solar System dynamics are what drew me into astronomy in the first place. More than any results of this paper, I find it absolutely stellar as it clearly explains what is being simulated, and why, and points the reader at additional sources of information on the particulars. In sense it manages to not only present the science that was done, but also how that science was accomplished.

My Scrawling Notes:

arXiv:1807.11442 - A Catalog of Spectra, Albedos, and Colors of Solar System Bodies for Exoplanet Comparison

Paper: A Catalog of Spectra, Albedos, and Colors of Solar System Bodies for Exoplanet Comparison
Authors: J. H. Madden, Lisa Kaltenegger

Abstract: We present a catalog of spectra and geometric albedos, representative of the different types of Solar System bodies, from 0.45 to 2.5 microns. We analyzed published calibrated, un-calibrated spectra, and albedos for Solar System objects and derived a set of reference spectra and reference albedo for 19 objects that are representative of the diversity of bodies in our Solar System. We also identified previously published data that appears contaminated. Our catalog provides a baseline for comparison of exoplanet observations to 19 bodies in our own Solar System, which can assist in the prioritization of exoplanets for time-intensive follow-up with next-generation Extremely Large Telescopes (ELTs) and space-based direct observation missions. Using high and low-resolution spectra of these Solar System objects, we also derive colors for these bodies and explore how a color-color diagram could be used to initially distinguish between rocky, icy, and gaseous exoplanets. We explore how the colors of Solar System analog bodies would change when orbiting different host stars. This catalog of Solar System reference spectra and albedos is available for download through the Carl Sagan Institute.

My Comment: This is cool stuff. In order to have a clue as to what we will (soon) be looking at in terms of exoplanets we need to know what the worlds that we have access to would look like as exoworlds. This (public) catalog is a nice first step. Clearly acknowledging several issues that arose in making it, it lays out a nice guideline as to how to make a first-pass at guessing if you are looking at a rocky or icy surface, or at a whole bunch of gas.  Also: Venus is hard.

My Scrawling Notes:

arXiv:1807.08322 -- Pre-airburst Orbital Evolution of Earth's Impactor 2018 LA: An Update

Paper: Pre-airburst Orbital Evolution of Earth's Impactor 2018 LA: An Update
Authors:C. de la Fuente Marcos, R. de la Fuente Marcos 

Abstract: Apollo meteoroid 2018 LA has become only the third natural object ever to be discovered prior to causing a meteor airburst and just the second one to have its meteorites recovered (at Botswana's Central Kalahari Game Reserve). Here, we use the latest orbit determination of 2018 LA (solution date 18-July-2018) to search for minor bodies moving in paths comparable to that of 2018 LA using the D-criteria, which are metrics to study orbit similarity, and N-body simulations. Our results further confirm the existence of a dynamical grouping of asteroids that might be related to 2018 LA and show that the impactor could be a recent fragment spawned by a larger object, the 550-m wide, potentially hazardous asteroid (454100) 2013 BO73. Spectroscopic observations of 454100 during its next flyby with our planet (brightest at an apparent visual magnitude of 18.4 on 2018 mid-November) may confirm or deny a putative similar chemical composition to that of the recovered meteorites of 2018 LA.

My Comment: A second very short letter (busy week this), but it does something very remarkable, very hard, and very needed -- attempting to link the space rocks on the ground to the rocks in space. For the most part all we can do is try to match spectra of meteorite samples in the lab to the reflectance spectra of asteroids in space. It is filled with many pitfalls. This is really neat as it gives a second diagnostic tool to work with - the dynamics of the impactor's orbit.

My Scrawling Notes:

arXiv:1807.08728 -- P/2017 S5: Another Active Asteroid Associated with the Theobalda Family

Paper: P/2017 S5: Another Active Asteroid Associated with the Theobalda Family
Authors: Bojan Novakovic

Abstract: In this note we have shown that a newly discovered comet P/2017 S5 (ATLAS), that moves around the Sun in an asteroid-like orbit, is a member of the Theobalda asteroid family.

My Comment: Super short letter, but packed full of references giving a clear "how you do this science" outline. Love it. One of my favorite experiences with an undergrad research student was when she serendipitously found a candidate active asteroid while working with me on a comet project. Turns out it (most likely) wasn't but working out that puzzle involved her getting time on a 3.5m telescope(!), and having her work praised by Jocelyn Bell Burnell(!!).

My Scrawling Notes:

arXiv:1807.02960 -- Outer solar system possibly shaped by a stellar fly-by

Paper: Outer solar system possibly shaped by a stellar fly-by
Authors: Susanne Pfalzner, Asmita Bhandare, Kirsten Vincke, Pedro Lacerda

Abstract: The planets of our solar system formed from a gas-dust disk. However, there are some properties of the solar system that are peculiar in this context. First, the cumulative mass of all objects beyond Neptune (TNOs) is only a fraction of what one would expect. Second, unlike the planets themselves, the TNOs do not orbit on coplanar, circular orbits around the Sun, but move mostly on inclined, eccentric orbits and are distributed in a complex way. This implies that some process restructured the outer solar system after its formation. However, some of TNOs, referred to as Sednoids, move outside the zone of influence of the planets. Thus external forces must have played an important part in the restructuring of the outer solar system. The study presented here shows that a close fly-by of a neighbouring star can simultaneously lead to the observed lower mass density outside 30 AU and excite the TNOs onto eccentric, inclined orbits, including the family of Sednoids. In the past it was estimated that such close fly-bys are rare during the relevant development stage. However, our numerical simulations show that such a scenario is much more likely than previously anticipated. A fly-by also naturally explains the puzzling fact that Neptune has a higher mass than Uranus. Our simulations suggest that many additional Sednoids at high inclinations still await discovery, perhaps including bodies like the postulated planet X.

My Comment: Fun discussion of solar system shaping mechanism and conducted further work to show plausibility of a fly-by during very early (10Myr) Solar System. Got me thinking about the Tisserand parameter with respect to Neptune, and once again am very happy to have astro-twitter folks willing to point papers and ideas out to me!

My Scrawling Notes:

Further investigation of changes in cometary rotation: arXiv:1806.11158

Paper: Further investigation of changes in cometary rotation
Authors: Beatrice E. A. Mueller, Nalin H. Samarasinha

Abstract: Samarasinha & Mueller (2013) related changes of cometary rotation to other physical parameters for four Jupiter family comets defining a parameter X  , which is approximately constant within a factor of two irrespective of the active fraction of a comet. Two additional comets are added to this sample in this paper and the claim of a nearly constant parameter X  for these six comets is confirmed, albeit with a larger scatter. Taking the geometric mean of X  for all the comets above excluding 2P/Encke (as X  for each comet was determined with respect to that of 2P/Encke), the expected changes in the rotation periods for a sample of 24 periodic comets are derived. We identify comets from this sample that are most likely to show observationally detectable changes in their rotation periods. Using this sample and including the six comets used to determine X  , we find a correlation between the parameter ζ  (i.e. the total water production per unit surface area per orbit approximated by that inside of 4 au) and the perihelion distance q  ; specifically we derive ζ  ∝  q −0.8   and provide a theoretical basis for this in Appendix A. This relationship between ζ  and q  enables ready comparisons of activity due to insolation between comets. Additionally, a relationship between the nuclear radius R  and the rotation period P  is found. Specifically, we find that on average smaller nuclei have smaller rotation periods compared to the rotation periods of larger nuclei. This is consistent with expectations for rotational evolution and spin-up of comet nuclei, providing strong observational evidence for sublimation-driven rotational changes in comets.

My Comment: The empirical law given seems to work on a factor of a few, which is better than the order of magnitude spanning effects being modeled. This paper does not justify its creation, with the details being presented in an earlier work from the authors in 2013.

My Scrawling Notes:

The New Horizons Kuiper Belt Extended Mission - arXiv:1806.08393

Paper: The New Horizons Kuiper Belt Extended Mission 
Authors: S.A. Stern, H.A. Weaver, J.R. Spencer, H.A. Elliott, the New Horizons Team
Abstract: The central objective of the New Horizons prime mission was to make the first exploration of Pluto and its system of moons. Following that, New Horizons has been approved for its first extended mission, which has the objectives of extensively studying the Kuiper Belt environment, observing numerous Kuiper Belt Objects (KBOs) and Centaurs in unique ways, and making the first close flyby of the KBO 486958 2014 MU69. This review summarizes the objectives and plans for this approved mission extension, and briefly looks forward to potential objectives for subsequent extended missions by New Horizons.

My Comment: Two and a half days before closest encounter, the extended mission target 2014 MU69 will finally be 2 pixels on the LORRI instrument. That's um... rather quick!

My Scrawling Notes:

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A year long Curiosity

Just a few quick thoughts.  This week marks the one year anniversary of the Mars Science Laboratory Rover, Curiosity, landing in Gale Crater on the surface of Mars.  A year ago we deposited a ton of nuclear-powered robot on the surface of another world. 

NASA/JPL-Caltech

Since then it is have been roving, scooping, dusting, vaporizing rocks, and just sciencing the heck out of the red planet.  36,700 images, 76,000 rock-zapping laser shots, and 1.6 kilometers driven so far.  It still has about an 8 km drive to go to get to the lower layers of the 5.5 km tall Mt. Sharp.  Just in it’s first year Curiosity has already a world that looks downright “habitable” in the distant past – spectacularly finding the remains of a pebbled riverbed.

NASA / JPL-Caltech / MSSS / PSI

So happy “birthday” to the MSL Rover Curiosity – may there be many more rocks to bother in your future.

Conjunction Junction, what's your function?

(My apologies to Schoolhouse Rock)

This weekend people around the world were treated to a very nice viewing of three planets all very close to each other in the sky.  An astronomical conjunction of the two interior terrestrial planets, Mercury and Venus, and the gas giant Jupiter.  Since I don’t want to get into the muddle of online digital image rights I took a screen capture of what the conjunction would look like from here in Virginia using the free open source planetarium program Stellarium.  You can tell it’s software since the planets don’t generally have large name labels when you look in the sky.



Neat huh?  All three planets are arranged in a triangle covering about 5 degrees of the sky (the whole pattern could be easily covered by your fist held at arm’s length).  Now this looks neat, but what is the importance of this event?  I mean while these planets are viewable together in a tightly compact portion of the sky they are still hundreds of millions of kilometers apart from each other and from the Earth.  What’s the significance?  Nothing… except the fact that we knew it was going to happen, and we can accurately determine when such alignments have happened in the past, and when they will happen in the future! 

For example, I can state with some certainty that the next time Jupiter and Saturn will be extremely close to each other in the sky will be on December 21st, 2020.  The last time these two gas giants were in conjunction was on May 31st of 2000.  Notice the time separation of 20 years.  This conjunction of Jupiter and Saturn happen about every 18 to 20 years because of the difference in times between the Earth’s orbit (1 year), Jupiter’s orbit (~12 years) and Saturn’s orbit (~30 years).  All of these worlds orbit round and round the Sun, and every now and then the math adds up just right and they are all in a line.  Not only do I know when this event will take place, but where it will be – the constellation of Aquarius.

Stop for a moment and think just how amazing that it that we can say such things.  We, people living on a small blue world, have the agency and know-how to accurately model, predict, and explain the motions of the planets, worlds unto themselves as they swiftly travel through space.  So what’s the significance of the conjunction?  Nothing but a beautiful demonstration of our exploration of the natural world around us.

Oh, and we’ve thrown robots at them as well.

Believing in comet dust

Well, I have a few things to add since my Comet Kerfuffle post a few months back.  Since then I've had the chance to take some images of comet C/2012 S1, aka Comet ISON through a fairly decent sized telescope (3.5 meter).  I'm starting to believe that we are in for quite a show this fall.  Why?  Well here's my reasons to be optimistic:


1.  At about 5 AU, where Jupiter orbits, the comet already has a very pronounced coma and tail.  This is still far enough out that it isn't getting warmed all that much by the Sun, and in fact not all of the gas species that drive the coma and tail have even reached sublimation temperature yet.  As one would would expect from an Oort Cloud object making a fresh return to the inner solar system, it is a very, very active comet.

Comet C/2012 S1 @4.9AU (Hammergren, Solontoi, Gyuk)

2. Its going to pass close to the Sun.  Really close.  Close enough that the tidal and thermal forces associated with the comet's passage by the Sun may cause it to fragment.  If that happens it will be quite a show for sure.  Unfortunately from the look of the orbit that event would most likely happen with the comet behind the Sun viewed from Earth.

3.  Folks who have been tracking the observed magnitudes of this thing are saying that it is fairly odd.  Most comets brighten suddenly and then "level off" at a certain point (if you're squinting at them in the right logarithmic axis!).  This one looks like it may have already gone through this change due to the way it is increasing in magnitude.  If that's the case it isn't a wild prediction to say that C/2012 S1 is trending toward "lunar" magnitudes - potentially as bright as the Moon!

Now I'm not saying that I am predicting that this is going to be a day-time comet - it will be hidden by the Sun when it is at perihelion for instance.  Many, many things can and will change in this comet's life between now and November of this year, but the way things are shaping up I am starting to really think that this comet will be spectacular in one way or another.

A Comet Kerfuffle

On September 24th a very faint comet was discovered in the constellation of Cancer at a distance from Earth of about one billion kilometers.  Now named C/2012 S1, or colloquially “Comet ISON” it has picked up quite a bit of press in the past weeks.  Looking at the orbit of this comet it certainly looks like it has the potential to be “spectacular” as seen from Earth.  It will pass close (within 1.2 million kilometers) to the Sun in late November 2013, and then pass by the Earth at about 40% of the Earth-Sun distance (~ 65 million kilometers).  The comet already seems to be active, that is showing some fuzziness as a result of gas and dust being liberated from its surface, even though it is still out beyond the orbit of Jupiter.  These two things have a whole lot of folks talking about this being a great comet, one that will put on a heck of a visible show in the night sky.  The idea being that this comet will produce a tremendous cloud and tail of gas and dust as it passes by the Sun, and will shine brightly in the night sky.  Some have even proclaimed that Comet ISON could put on a show similar to that of the Great Comet of 1680. Or, you know, it could be a total dud, viewable by almost none <cough Kohoutek cough>

The Great Comet of 1680 by Lieve Verschuier

Now, how can people on one had be comparing this comet to very visible, spectacular looking comets like the Great Comet of 1680, or even Comet Hale-Bopp, yet at almost the same time caution that we may end up seeing nothing?  It all has to do with how a comet behaves, and how unpredictable that behavior actually is.

What we see of the comet in the sky is not the object itself: The actual comet is a small, dark, potato-shaped object made up of rocks, carbon, and ices.  In 1950 Fred Whipple described comets as “Dirty Snowballs,” and that’s how we still see them, although recent observations, and fly-bys of several comets have me leaning toward calling them“Icy-Dirtballs” to better describe them.  As these objects (the comet nucleus) nears the sun, many of the ices near the surface will vaporize, producing a “coma” or cloud of gas and dust around the comet.  This is what we see when we look at the head of a comet.  This gas and dust interacts with the solar wind and gravity and eventually produces tails for the comet, completing our mental image of what a comet is.

That said, the exact processes and amounts of gas and dust to be liberated are unknown quantities on a comet-by-comet basis.  How much ice is left near the surface from previous passages through the solar system?  How deep can the Sun actually warm the comet?  Will the comet crack, or break apart under the gravitational and thermal stresses as it passes by the Sun?  Will a large amount of dust be liberated with the vaporizing gasses?  All of these questions play a vital role in determining how a comet will look in the sky.  A very gassy, dusty comet that dredges up material from deep within could put on quite a show.  At the same time, one that only vaporizes a thin surface layer of ice could certainly be a “dud” for the eyes (although it could still have quite a bit of scientific value!).

So what will happen in late November 2013 when Comet C/2012 S1 comes by?  No one has any clue, but we may get lucky and have a really nice comet hanging in the sky at the end of that year.  Or not.

Yes Virginia, you can see the flags on the Moon!

One of the all-time questions that people ask about any big telescope is “can you see the flags on the Moon?”  The answer for all ground based, and Earth orbiting (e.g the. Hubble Space Telescope) is no for a variety of reasons: too small at that distance, on too bright of a surface, etc.  In fact the Hubble website has this question (with answer)  in their FAQ!  With the fantastic images from the Lunar Reconnaissance Orbiter Camera (LROC) in Lunar orbit however, we can indeed see many of the objects left behind by the Apollo astronauts.  The landers, footpaths, rovers, and science experiments are all visible in amazing detail.  For example, below is a recent LROC image of the Apollo 11 landing site at the Sea of Tranquility.

LROC image credit NASA / GSFC / ASU 

But what about the flags?  Now in many of the images there seems to be something around where the flags were planted, but it’s really tough to tell anything about them from a single image.  Even with shadows, it is hard to make out if the shadow is from the flag, or from the flagpole!  Quite a number of people, myself included, have postulated that the flags on the Moon have deteriorated away during the 4+ decades that these flags have been there.  Harsh UV, charged particle, and micrometeorite bombardment – all things that our atmosphere and magnetic field protect us from – might have easily destroyed a standard nylon flag, which indeed was all that the Apollo flags were.

That said, you can indeed make out the “flag” site of most of the Apollo landings in the LROC images, and something is there!  But are they the flags, or just the poles with a pile of nylon dust?  A recent round of LROC observations has answered that question:  Despite my pessimism on their survivability, the flags are still there.  Having now observed the landing sites at many angles, the LROC team has been able to look at the shadows cast by the flags, and those shadows not only match those expected by a flag+pole, but change orientation with the sun from image to image!  Below is a recent image of the Apollo 17 site, along with a blow-up of the portion with the descent stage and flag – that shadow is certainly more than just the pole!

LROC image credit NASA / GSFC / ASU

The LROC team has also made an animation out of the still images of the Apollo 12 site, you can watch the shadows move around during a “lunar day” reconstructed from the LROC observations:

Ok, to be fair, the flags might not be intact.  While we can now see that they are still standing, the 40+ years they’ve spent on the Moon may have “bleached” out their colors, but it’s still pretty flipping cool that 5 out of 6 Apollo Flags have been found.  Buzz Aldrin mentioned that he thought he saw the flag get knocked over as he and Neil Armstrong took off from the Moon, and what do you know, he was right.  The only Apollo flag not identified in the LROC images is Apollo 11’s.

And then there were five…

134340 Pluto has a new moon, bringing the distant dwarf planet’s collection of satellites to 5.  No official name for the little guy yet, but this 10 to 25 km piece of (more than likely) ice takes about 20 days to orbit Pluto at a distance of about 42,000 km, placing it between Charon (the largest and innermost know moon) and Nix.  With the New Horizons probe on the way to Pluto, the little world’s family of moons continues to grow.

Pluto’s system of five moons.  Pluto and Charon are added into this composite image from a different source – the light from them needs to be blocked in order to make out the much fainter satellites.

Pluto’s first satellite, Charon was discovered by James Christy in 1978.  He noticed a “bump” in the images of Pluto that changed position (and even disappeared) from image to image.  Since then studies of Charon has allowed for much better mass measurements of Pluto, as well as revealing information about the moon itself.  Charon is, in relation to its parent, the largest object we consider a “moon.”   Charon’s diameter is about half that of Pluto, with 12% the dwarf planet’s mass.  Compare that to the Earth-Moon system: our Moon is about a quarter the diameter of the Earth in size with only 1.2% of the mass of the Earth, and our Moon is abnormally large compared to most planetary satellites (e.g. Saturn’s largest moon Titan is about than .02% the mass of Saturn!).  Charon is so massive compared to Pluto that it causes Pluto to actually orbit a point ouside of itself in space.  Really Pluto-Charon could be considered a double dwarf planet (or a binary Kuiper Belt Object) as they both orbit around a point partway between each other.

Now you see me now you don’t: The “bump” that would become known as Charon is visible to the upper right of Pluto in the first image, but not in the second.

Charon and Pluto are also tidally locked to one another, Pluto’s rotation, the rotation of Charon and the the orbit of Charon all take the same amount of time, roughly 6 days, 9 hours.  This situation results Pluto and Charon always “facing” each other.  Charon will always be in the same place in the sky for an observer on Pluto (and the other way around too!).


The rest of Pluto’s family of satellites are more recent discoveries.  The dwarf planet had been under detailed study to prepare for the New Horizon’s mission, which was launched in 2006, and is scheduled to fly-by Pluto and its moons in 2015.   By blocking the light from the bright sources of Pluto and Charon, the region near Pluto may be searched for additional, small and faint bodies.  In 2005 a team conduced a search for companions of Pluto using the Hubble Space Telescope and discovered two new satellites of Pluto, later officially designated Nix and Hydra.  In 2011 a 4th moon of Pluto was discovered, “P4”  Which brings us up to today, with the recent announcement that a 5th moon of Pluto, “P5” had been identified through HST images.  All four of these newer moons are pretty small, with the largest one, Hydra, between 60 to 170 km across, while the smallest moon,  the newly discovered “P5,” being only 10-25 km in diameter.  Quite a bit of the uncertainty in size comes from not knowing how reflective these moons are.  If they have very dark surfaces, they will be larger than if they had very reflective surfaces since these size estimates are based on how bright the sunlight is that has reflected off of their surface and been collected by our telescopes.


Of interest is the relationship that the orbits of Pluto’s moons have with each other.  They are all very close to mean motion resonances with the Pluto-Charon system.  From closest P5, Nix, P4, and Hydra are almost in a 1:3:4:5:6 resonance with the Pluto-Charon.  That means that every 6th time Charon orbits Pluto, P5 will have completed 5 orbits, Nix will complete 4, P4 will have completed 3 and Hydra will have finished one orbit of Pluto.  Details are being studied right now, but it seems as though none of them are in a “perfect” resonance – but the orbital dynamics of the Pluto system are getting very interesting indeed.


In fact a colleague of mine, Dr. Alex Parker at the Harvard–Smithsonian Center for Astrophysics, has made a wonderful demonstration of how close to resonance these moons are.  By translating their orbital frequency into sound, and boosting it by 29 octaves (to be in the auditory range) Dr. Parker has turned the Plutonian orbits into “music”.  One can visit his SoundCloud page: http://soundcloud.com/alexhp-1/plutos-five-moons and hear the slight difference between a perfect resonance, and what we have measured the Plutonian system to be in.  Seriously, check it out – it is super cool.

Flag Day - The Updating!

Turns out I’ve already got an update to my Flag Day! post from a little bit ago.  I had speculated that like Pathfinder, the flag decals on the Mars Exploration Rovers, Spirit and Opportunity, were under the camera-mast, and thus not imaged by the rovers.  Boy was I wrong!

Here’s the flag on the instrument deployment device (IDD), the rover’s “arm” on Opportunity.  All that dust on the instrument is left over from using its rock abrasion tool (sort of a grinder/drill) on the exposed rocks during Opportunity’s 31^st Martial day.

I also missed an obvious “2-fer” on Spirit!  Beyond the decal on the IDD, Spirit also carried with it a memorial to the crew of the Space Shuttle Columbia, STS-107. 

The above memorial plaque carries the US flag, along with the names of the Astronauts who were lost on the Columbia.  If you look closely you can see an additional Israeli flag next to the name of Ilan Ramon, Israel’s first astronaut.

As a bonus here’s a shot of the first “nationally branded” object deployed to the surface of the Moon

These two steel spheres (diameters 7.5 and 12 cm respectively) were carried to the Moon by the Soviet Union’s Luna-2 spacecraft.  Each of these spheres was filled with a an explosive designed to fragment them like a very large grenade, showering the Lunar surface with the little pentagonal pennants that the spheres were crafted out of.  It is really unlikely that any of these little medals survived.  On September 13, 1959 Luna-2 didn’t land gently on the Moon, but rather plowed into it at over 3 km/s.  The energy generated by the impact of a 400kg spacecraft at the speed would generate enough heat to vaporize steel.  One of the ideas behind the explosives inside the spheres was to try and remove some of the impact velocity, and thus allow at least some of them to survive.  It’s possible but, in my opinion, unlikely that they made it through the impact intact.

The first Soviet Moon probe, Luna-1, also carried a similar sphere, but missed the moon (Luna-1 passed within 6,000 km of the Moon on January 4, 1959), and is now in a 450 day orbit about the Sun.

New stuff from really old rocks.

A recent article in caught my (and several other people’s) eye. Chi Ma, et al., “Panguite, (Ti⁴⁺,Sc,Al,Mg,Zr,Ca)_1.8 O₃, a new ultra-refractory titania mineral from the Allende meteorite: Synchrotron micro-diffraction and EBSD,” American Mineralogist , July 2012, v. 97, no. 7, p. 1219-1225.  Now I’m not a geologist.  Most of the “meteorites” that I study are still in space, and I don’t know the author at all.  Why am I excited about it?  Therin lies the story…

On February 8, 1969 thousands of rocks fell from the sky over an area some 300 km² is size near the village of Pueblito de Allende in Chihuahua Mexico.  Now known as the Allende meteorite, it stands as one of the most famous and important meteorites in modern times.  Why is that?  Well Allende’s main claim to fame is that it extremely primitive, or in other words, it is really honking old, and is basically unchanged from the earliest times of the Solar System.  It is known as a carbonaceous chondrite, a class of meteorite that are very dark and rich in volatiles like water and (sometimes) organics.  Some carbonaceous chondrites have been known to sweat water when heated.

The fact that these meteorites exhibit that trait indicates something striking – they were never part of a very large parent body (asteroid).  If that was the case the heat generated by the formation of slamming all these small rocks together, and the mutual heat generated by the natural decay of radioactive nucleotides would have radically changed the composition of these rocks.

Allende in particular is know to have in it many, tiny, little white bits trapped within the generally dark matrix that makes up the bulk of Allende meteorites.  These little white bits are called calcium-aluminium inclusions, or CAIs. 

Above is a slice of Allende with a couple prominent CAIs visible.  It is these CAIs that hold the Solar System’s clock.  They were the (some of) the very first high temperature solids to form in the Solar System.  When someone says that the Solar System is 4.57 billion years old, they are really saying that these first solids (the CAIs) formed that long ago (age “zero” for a rock is when it crystalizes/becomes solid).  Essentially, meteorites like Allende are the left over building blocks of the Solar System.  Put enough together you get Mercury.  Put enough together you get Mars.  Put enough together and you get the Earth.  They are the most primitive bits of Solar System solids, older than any rock we can find on large bodies like the Earth, Mars, or even the Moon.  These CAIs have basically the same elemental composition as the early Sun (excluding gasses of course), and CAI bearing meteorites like Allende preserve these pre-Solar System grains - samples of what the Solar System itself was like almost 4.6 billion years ago!

Now, back to the Chi Ma, et al., 2012 paper.  Take apart the title and you have the story: they found a brand new high temperature mineral, now officially named “Panguite,” in samples of Allende.  The same Allende that fell in Mexico in 1969, was collected and has been studied for over 40 years!  Allende, one of the most famous and well studied meteorites in history still has many secrets to reveal – and that’s one of the things that makes planetary science, astronomy, and science in general, great to me:  It always has some new way of surprising you, whether it is bizarre, unexpected features on the first images of a new world or brand new minerals being found in rocks that have been continually studied for half a century.

Science just plain rocks.  Sorry, had to make the obligatory geology joke there.

Panguite is ready for its close up as seen in Figure 2 from Chi Ma, et al., 2012.