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Expanded-color image of Mercury’s 52-km Degas crater, showing an abundance of dark material (NASA)

Today brings interesting color themed news from outer space. The Messenger space craft (which was destroyed when it was deliberately crashed into Mercury in spring of 2015) spotted numerous mysterious dark spots on Mercury. Indeed the Messenger spacecraft probably now is a dark spot on Mercury. Apparently the small dense planet has a dark layer close beneath the surface. Asteroid impacts, volcanoes, space probe collisions, and other events which disturb the surface of the planet reveal this extremely dark black/gray layer.

Scientists have been analyzing the data from Messenger and it now seems that this black layer which is the color and texture of pencil lead is actually composed of…graphite, the same material as pencil lead! Apparently when Mercury formed (which featured strange geological processes unseen anywhere else in the solar system) a planet-sized ocean of lava covered the entire world. As Mercury cooled the heavier elements of this lava field crystallized and sank leaving the buoyant pure carbon at the top. This dark layer has been subsequently covered with ejecta, dust, and fragments, but any disruption shows the crystallized carbon is still there.


Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

There is a lot more data from Messenger left to analyze. I wonder what other surprises the closest planet to the sun still holds.

Artist's conception of MESSENGER above Mercury (NASA)

Artist’s conception of MESSENGER above Mercury (NASA)

On Thursday, humankind is deliberately crashing a spaceship into another planet! We could easily be the evil aliens in someone else’s space drama. Well, at least we could be, if there were any remote chance that Mercury, the intended target of our bombardment, were a possible haven for life.  And bombardment is not really the right word: what is actually scheduled is the seemly & rational conclusion to NASA’s MESSENGER mission, a highly successful exploration of the solar system’s mysterious innermost world.  The mission has been ongoing for more than a decade (a decade of our Earth time—or nearly 40 Mercury years).

A portrait of Mercury from MESSENGER

A portrait of Mercury from MESSENGER

The 485-kilogram (1,069 pound) MESSENGER spacecraft was launched from Cape Canaveral in August 2004. The space probe has an awkward and contrived government acronym, which is why I keep talking about it in all caps—I’m not shouting (although planetary exploration does make me very excited). The craft took some amazing pictures of Venus (a planet which always calls to me) on its way to Mercury.  Then MESSENGER flew by the small planet multiple times before entering orbit on March 18, 2011 (the first human spacecraft to do so).  Since then MESSENGER has extensively scanned and mapped the surface of Mercury—a planet which is surprisingly elusive to astronomers because of its proximity to the sun.  The mission revealed some surprising results which are leading to big new questions.

False Color Maps of Mercury (NASA)

False Color Maps of Mercury (NASA)

Mercury has a small diameter—it is actually smaller in area than some of the moons of Saturn and Jupiter—but it has substantial mass because much of it is made of heavy metals.  The face of the small world is thought to be ancient: scientists speculated that its bland pitted face might date back to the formation of the solar system, but it seems that Mercury does harbor secrets.

The mission featured a big surprise.  Messenger found surface water in the form of ice frozen inside the polar craters of Mercury.  This was not really a shock—astronomers have suspected that ice was present due to radio-telescope readings.  What was surprising was that the ice was coated with tarlike black goo. My poor roommate (who is always wandering the house pointing at films, stains, and accretions in horror) would not be surprised by a black coating on anything, however scientists were taken aback because Mercury was not thought to have any “volatile” compounds.  According to the current models of planetary formation, elements like chlorine, sulfur, potassium and sodium should have boiled away during the cataclysmic high-temperature formation of Mercury…yet there they are, like the scum in my kitchen. The scientific data from MESSENGER is likely to force a rethink of planetary formation (although frankly, considering all of the weird exoplanets that are being discovered, scientists probably need to refine their theories about planetary accretion anyway). The mission also measured subtle planetary flux which should give us a better sense of Mercury’s composition and internal workings.

The yellow patches show areas where water ice is believed to exist. (NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

The yellow patches show areas where water ice is believed to exist. (NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

All good things must end, however, and MESSENGER has run out of fuel for maneuvering.  Mission controllers have opted for an operatic exit and they are smashing the craft into the planet’s surface at 8,750 miles per hour (nearly four kilometers per second).  This should create an 18 meter (50 foot) wide crater.  Future scientists will have a known fresh disturbance to use as a benchmark for assessing the ancient craters of Mercury.  Perhaps the plume will reveal some interesting secrets as well.

MESSENGER Crashes into Mercury (Wayne Ferrebee, 2015, ink and colored pencil)

MESSENGER Crashes into Mercury (Wayne Ferrebee, 2015, ink and colored pencil)

Unfortunately, it will be a while before we see the results of our destructive acts.  The site of impact is hidden from Earth, and we have no other spacecraft in any proximity to Mercury. A European and Japanese collaboration called BepiColombo is scheduled to launch from Earth in 2017 and arrive at Mercury in 2024.  Perhaps we will have new questions for whatever answers MESSENGER is about to divulge in its unseen but spectacular final act!

Update: Through some grotesque oversight, NASA failed to portray MESSENGER’s final moments through the magic of art. I took the liberty of providing my own interpretation above.  NASA did not return my questions about whether the spacecraft will wail in a plaintive manner as it impacts the surface–so I am forced to assume that it will.  Did I mention that Mercury has no atmosphere?  You should probably ignore that…

The Dwarf Planet Haumea

The Dwarf Planet Haumea

Haumea is a dwarf planet located in the Kuiper belt.  The little planetoid was discovered in December 2004 by a team of Caltech astronomers.  It is about a third the size of Pluto.  The team initially called it “Santa” but, in keeping with the IAU’s naming convention for Kuiper belt objects they eventually named the worldlet after a matronly fertility goddess from Hawaiian mythology.

Artist's conception of Haumea and its pink spot

Artist’s conception of Haumea and its pink spot

Although Haumea is typical of other dwarf planets in the Oort cloud in that it is a hunk of rock covered with ice, there are a couple of very unique things about the body.  Most notably Haumea is shaped like a lozenge (as opposed to being mostly spherical like other planets).   Astronomers believe that Haumea has sufficient gravity to overcome the compressive strength of its material.  In other words it chould be approximately spherical, however the planet is rotating with such velocity that it has become spindle shaped—like a water balloon thrown in a rifling spiral.


The extreme rapidity of Haumea’s rotation is its other defining characteristic.  It rotates more rapidly than any planetlike object with a diameter greater than 100 kilometers.   Haumea rotates completely every 3.9 hours so days there are incredibly short (although its huge orbit takes 283 years to complete—so years are long).  It is believed that Haumea’s breakneck spin comes from a titanic collision with some other Oort belt object.  Haumea’s two dinky moons were probably also created by the impact.  Haumea has a large red spot on it–perhaps because of the presence of minerals–or the fractured perturbance left by an impact.

Ferrebeekeeper has already posted about the aegis, the invulnerable shield of Jupiter/Zeus, which was fashioned by the king of the gods from the skin of his foster mother (and loaned to his favorite daughter.  However the concept of Jupiter’s shield has a larger significance.

Yesterday morning, an unknown object appears to have slammed into the planet Jupiter.  Oregon based astronomer Dan Petersen was watching the gas giant at 4:35 AM PST (September 10th, 2012) when a bright flash erupted from near the Jovian equator.  Another amateur astronomer, George Hall of Dallas, TX was filming the planet through his 12 inch telescope and recorded the flash (you can see the video here).

The September 10th, 2012 Flash on Jupiter (recorded by George Hall)

Thanks to the florid nature of science fiction entertainment, it is easy to imagine scaly green Guarillions testing out energy weapons against the huge planet, but the flash was almost certainly from a comet or asteroid striking the surface (we will know more as astronomers look at Jupiter this week).  Such impacts have proven to be much more common than imagined.

Jupiter has a mass of approximately 1.9 x 1027 kg (which is equivalent to 318 Earths).  The gas giant is 2.5 times more massive than all of the rest of the non-sun objects in the solar system added together. The sun itself comprises between 99.8% and 99.9% of the mass of the system (which should put some perspective on the precision required for our ongoing programs to scan the nearby galaxy for exoplanets).

Jupiter Relative to the Sun and the Earth (NASA Goddard Space Flight Center)

The huge mass of Jupiter (relative to other planets and moons) means that a great many asteroids, comets, meteors, and whatnot fall into its gravity well.  Were it not for Jupiter, these hazardous leftovers would otherwise fly all around the solar system willy-nilly knocking holes in things and creating unsafe conditions (just ask the poor dinosaurs about this).  The ancient myths of the Aegis provide a powerful metaphor for this protection. Jupiter does indeed provide a shield for the smaller planets:  If it did not suck up so many cosmic punches, who knows if life could even have survived?

(Lithograph by F. Heppenheimer)

In the impact crater of a giant meteor, an unknown ancient race built the largest snake effigy on the planet… Is this the beginning of a lurid sci-fi fantasy novel? No, it’s the description of an actual place.  This haunting structure which was built for unknown reasons by a mystery race can be found in deepest…um…Ohio!

The Great Serpent Mound is an ancient earthwork located in Adams County, Ohio.  Shaped like a snake devouring an egg, the mound is 410 meters (1,330 feet long) and a meter tall (3 feet).  The undulating form of the snake has been tied to astronomical phenomena but it is unclear why it was built or what purposes (if any) it served. It reminds me somewhat of the Rainbow Serpent, Wadjet, Nüwa, and other snake deities, but since there is no historical or ethnological record of its purpose, such connections are only airy speculation.

Possible Astronomical Significance of the Great Serpent Mound

An even greater mystery of the structure is who built it. Over the years scholars and archaeologists have variously posited that it was created by the Adena culture (1000 to 200 BC), or by tribes from the Hopewell tradition (200 BC to 500 AD), or by the Fort Ancient culture (1000 AD-1750 AD).  Of course the mound was known long before its “discovery” by European settlers. Unfortunately, the Native Americans of the region seemed just as confused about its provenance as anyone. For what it is worth, Native Americans of the Lenni Lenape (later Delaware) nation told missionaries that the mound was built by the Allegheny or Allegewi People, (who were also sometimes called the Tallegewi), a possibly mythical progenitor race who lived in the Ohio Valley in ancient times before 1200 BC.

The Great Serpent Mound from the Air

It is obvious that a date is thoroughly confused when it varies by as much as 3,000 years! Fortunately there are a few pieces of actual evidence associated with the mound. Adena graves were found and excavated near the Serpent Mound (Adena people were culturally and physically distinct from other peoples of the Ohio valley). Other Adena sites have revealed that these peoples built elaborate circular and winding earthworks and had a fascination with astronomical phenomena. The few pieces of Aedena art even seem to bear an aesthetic connection.

A Serpent Carved from Micah by the Adena or Hopewell

Frustratingly, carbon dating of charcoal taken from within the mound seems to indicate that it was built (or at least refurbished) long after the Adena culture declined and vanished. Conducted in the nineteen nineties, these tests indicated that parts (or all) of the Serpent Mound was built around 1070 AD.  The mound would thus have been made by people of the Fort Ancient Culture–but the Fort Ancient people do not seem to have evinced the same artistic and cosmological sensibilities as are reflected in the mound.  Additionally the mound was uncharacteristic of Fort Ancient culture in its lack of buried valuables.

A painting of Fort Ancient Civilization

Charcoal fragments are easily displaced by bioturbation and burrowing animals, so the carbon dating stands in question. The Fort Ancient people are known to have had contact with the intense pyramid building, city-dwelling (serpent worshipping) Mississippian cultures which were flourishing from Illinois down to the Gulf of Mexico. Perhaps outside cultural influences lead to the mound’s construction. Furthermore the Fort Ancient people got their name from the fact that they lived on huge earthworks built by the vanished Hopewell people (who are also potential builders of the Great Serpent Mound). Perhaps the Fort Ancient tribes also renovated and re-purposed the Great Serpent Mound from older Adena or Hopewell builders.  We simply are not certain about who crafted the Great Serpent Mound–but it is to be hoped that further evidence will clarify the issue.

By now space enthusiast readers are probably chaffing at all of this human history: in the first paragraph I mentioned that the Great Serpent Mound is located in a meteor impact crater. relates how the crater was discovered by scholars studying the Great Serpent Mound:

After the mound was discovered it was noticed that the geology of the surrounding area differed greatly from that found elsewhere in Ohio. John Locke, who explored the area in the 1830’s noted that “a region of no small extent had sunk down several hundred feet, producing faults, dislocations and upturnings of the layers of the rocks.” At the time he thought the he had discovered a “sunken mountain.” Some of the areas look like they have slid straight down while others have risen almost 1,000 feet straight up. Over time more evidence has been found. Eventually in the 1970’s, core samples were taken from the crater area. Scientists have found iridium at levels up to 10 times that normally found in the Earth’s crust, soot from what may be scorched limestone, deformed grains of sand, and quartz with microscopic fractures. In addition “shatter cones” have been found from the surface down similar to those found in Nevada at nuclear weapon test sites.  

Such features are the smoking gun evidence of meteor strikes and scientists have since concluded that the crater is about 250 million years old (which was approximately the same era the Paleozoic came to an end). Over a quarter of a billion years the crater has deformed greatly, to such an extent that it is not immediately recognizable (unlike more contemporary strike sites such as Lake Lonar).

Lake Lonar

Approximately 650,000 years ago, an outer space object–either a comet or a meteor– struck the Deccan plateau (an immense basaltic flow on the Indian subcontinent dating back to the twilight of the dinosaurs).   The resultant crater in Maharashtra is now the sight of a very interesting saltwater lake, Lake Lonar.  The geology of this region has been intensely studied because the great basaltic mass of the Deccan traps is thought to mirror the igneous geology of Mars and the moon.

Lake Lonar proper is nearly circular with a diameter of 1.2 kilometers.  The greater meteor crater rim is about 1.8 kilometers and the crater measures 500 feet deep in the deepest part of the lake.  In addition to the obvious features of an extraterrestrial impact (um, a large round hole), the region features many other unique geological signs of such an event. Maskelynite, a material only naturally known from meteorites and meteorite impact areas, is found around Lake Lonar, as are silicate minerals with planar deformation features (distinctive high-stress crystalline irregularities which have only been found in silicates from meteorites, craters, and nuclear test areas).  The deeper geology of the lake region displays shatter cones in the bedrock, and extreme deformation of the basalt layers. Finally the surrounding region has been spattered with a non-volcanic ejecta blanket. 

Lake Lonar: pink-beige indicates bare ground, blue and off-white indicate human-made structures, dark blue indicates water, green indicates vegetation, and dull purple indicates fallow fields (NASA: Terra Satellite)

By measuring the accumulated radiation in certain crystals (aka thermoluminescence) scientists had assigned an approximate age of 50,000 years to the crater. However a 2010 study of isotopic Argon in Lonar impact melt rock estimated the true time of impact to be 650,000 years ago (give or take 80,000 years).  The compelling 2010 study drily notes “The discrepancy between the thermoluminescence age and the new isotopic 40/Ar/39Ar age is flagrant.”

Daitya Sudan, a temple to Vishnu

Several abandoned temples and archaeological sights are also located around the lake.  For example, the beautiful Daitya Sudan Temple to Vishnu was built by the Chalukya Dynasty which ruled of Maharashtra from the 6th and 12th centuries.  The local town, Lonar, still has an active temple to Vishnu, the great protector of the universe who features prominently in local legend.  According to the Skanda Purana (a canon of Hindu scripture universally cited when a story is doubtful or can not be found elsewhere) a great underworld demon, Lonasur, lived where Lake Lonar is today.  From time to time the demon would venture from his subterranean abode to torment the countryside and challenge the gods. Assuming the form of an extremely beautiful young man, Vishnu…somehow convinced the demon’s sisters to divulge where the monster could be found.  The god then lifted up the countryside like a great lid and found the demon hiding in his huge circular lair. After Vishnu slew the demon, the demon’s dwelling place filled up with water made salty by the fiend’s blood.    

Although threatened by India’s ever growing sprawl, Lonar Lake is a rich wetland with abundant wildlife—particularly birds.  The jungles, fields, and lake are a birder’s paradise featuring flamingos, grebes, black-winged stilts, dabchicks, ducks, shell-ducks, shovellers, teals, herons, rollers, parakeets, hoopoes, weavers, larks, tailorbirds, magpies, robins, swallows, peacocks, coots, white-necked storks, lapwings, grey wagtails, black droungos, green bee-eaters, and tailorbirds (to name just some).

The Jungle around Lake Lonar

Mimas (Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA)

Mimas is a moon of Saturn.  Discovered late in the 18th century by the astonishing Sir William Herschel, Mimas is the smallest (known) astronomical body which is spherical from self-gravitation (here is an explanation of what that means).  The moon’s most noteworthy feature is an enormous impact crater named Herschel which is 130 kilometres (81 mi) across–about the same as the distance between New York and Philadelphia. Wikipedia gives some additional dimensions of the crater:

Herschel’s diameter is almost a third of [Mimas’] diameter; its walls are approximately 5 kilometres (3.1 mi) high, parts of its floor measure 10 kilometres (6.2 mi) deep, and its central peak rises 6 kilometres (3.7 mi) above the crater floor.

If you were standing in the crater (which you should not do!) it would be a great broken plain surrounded by cliffs thirteen times taller than the Empire State Building.  In the middle you could see a huge mountain slightly shorter than the tallest mountain in North America.  Jagged craters and valleys as deep as Lake Baikal would lie around you.

Mimas orbits above Saturn. The dark lines are shadows cast by the rings (Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA)

A great series of impact cracks on the opposite side of the moon would seem to indicate that the collision which created Herschel nearly shattered Mimas (which is composed principally of ice).

The moon’s name might be of passing interest to followers of my Deities of the Underworld category. In Greek mythology, Mimas was one of the monstrous sons of Gaia.  He was born with snakes for legs and he was clad in full armor.  In the Aeneid, Virgil tells the story of how Hephaestus imprisoned Mimas under Vesuvius during Gaia’s great rebellion against the Olympian gods.  As the imprisoned giant shakes so to does the area around the Bay of Naples.

Mimas--Yikes! (Also, what happened to his armor?)

As I was researching this article, I was struck by how many moons Saturn has! As a special bonus feature, here is an alphabetic list of Saturn’s named moons (several more remain anonymous): Aegaeon, Aegir, Albiorix, Anthe, Atlas, Bebhionn, Bergelmir, Bestla, Calypso, Daphnis, Dione, Enceladus, Epimetheus, Erriapus, Farbauti, Fenrir, Fornjot, Greip, Hati, Helene, Hyperion, Hyrrokkin, Iapetus, Ijiraq, Janus, Jarnsaxa, Kari, Kiviuq, Loge, Methone, Mimas, Mundilfari, Narvi, Paaliaq, Pallene, Pan, Pandora, Phoebe, Polydeuces, Prometheus, Rhea, Siarnaq, Skadi, Skoll, Surtur, Suttung, Tarqeq, Tarvos, Telesto, Tethys, Thrym, Titan and Ymir.

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August 2020