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.

Short Break!

Lots of stuff going on - I've got blog snippets about images of Earth from other Worlds, cool results from LRO about the Apollo flags still standing on the moon, and of course MSL Curiosity landing on Mars, including the NASAsocial (tweetup) at the NASA Langly Research Center prior to the entry, descent, and landing portion of the MSL mission.  It is also almost time for courses to begin and I'm putting the wraps on my Fall Solar System course, so that's been where most of my writing time has gone.  I'll have some official babbling on stuff again real soon.

Home library organization

Well, the moving truck finally brought our stuff to us in Virginia, and that meant it was time to organize and shelve all of our books.  How to do it?  By subject?  By author?  By color?  By sum of all ISBN digits? By how loud the book is when dropped from 4.5 feet?  Well being the giant academic nerd that I am, I suggested “why not just use the Library of Congress?”  We did.

Now really, even though my family has a lot of books, we don’t have nearly enough to call what we have “a library,” and so the Libraray of Congress system isn’t exactly a perfect fit, but it made the decision for us, and it was both a little fun, and turned up a couple of surprises along the way.  Here are a couple that stood out while we were sorting and shelving:

Anthony Bourdain, the opinionated trash-talking chef and travel guide of No Reservations (among other shows) has written a number of books about his career and experiences as a chef and world traveler.  Where does the LoC put his books? Why TX – Home Economics of course!

The Physics of Christmas by Roger Highfield gets put into GT - Manners and Customs, as the subject has been determined to be 1. Christmas and then 2. Science.  Also in the G section (subsection GF - Human ecology. Anthropogeography) are the The Worst Case Scenario Survival Handbook line of books.  Except, oddly enough, The Worst Case Scenario Survival Handbook: Work  Which ends up in PN - Literature (General).

Historical creative non-fiction also end up in weird places.  The creative non-fiction The Perfect Storm by Sebastian Junger gets sorted into QC – Physics, and Seabiscuit: An American Legend by Laura Hillenbrand goes into SF - Animal husbandry, Animal science.

Now I’m not a librarian, nor do I have any training in library science.  I’m not knocking the classification system here at all – in fact I may have even been poorly informed by the various search engines I used to look up the LoC classifications for my books that didn’t have them printed on the copyright page.  I’m just an astronomer with a couple bookcases of books who is rather amused by where this classification scheme puts some of them.  With that disclaimed I’ll sign off with one last placement oddity: The Pursuit of Happyness by Chris Gardner (now a movie starring Will Smith) gets filled under HG – Finance.

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.

Off the air for a week or so.

A Sky Full of Rocks will resume its normally sporadic schedule later this month.  I’m moving across the country and will be at the whim of when the cable folks show up to the new place.  That said, cool stuff is happening, from the CERN / Higgs Boson stuff on the 4th of July, to the MSL Curiosity Rover’s landing on Mars on August 6th, and bunch of things between then too.

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.