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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…

A day ago an international team of stellar physicists announced that the sun’s surface is covered with thousands of searing hot plasma super tornadoes each of which is the size of a large continent on Earth.  Using a combination of a space telescope and a ground telescope, researchers discovered that each of these plasma vortexes spins at velocities up to 14,500 kilometers (9,000 miles) an hour.

(CREDIT: Wedemeyer-Böhm: Parts of the image produced with VAPOR)

The mystery of why the corona of the sun is 300 times hotter than the star’s surface has long vexed scientists.  The surface of the sun is a balmy 5,526 degrees Celsius (9,980 Fahrenheit), while temperatures in the corona peaks 2 million degrees Celsius (3.5 million Fahrenheit). The discovery of these giant fast-moving storms provides a new mechanism by which heat is transferred through the sun’s atmosphere and ejected into the corona. Energy locked in the powerful magnetic vortexes is effectively self-insulated and does not heat the solar photosphere and chromosphere as much as the corona (where the storms widen and dissipate).

The Sun photographed by the Atmospheric Imaging Assembly (AIA 304) of NASA’s Solar Dynamics Observatory

Sven Wedemeyer-Böhm, a Norwegian scientist working on the team was quick to stress that the tornadoes are likely one of several complicated energy transfer mechanisms by which heat reaches the solar corona. However it seems that there are more than 11,000 of these huge plasma tornadoes on the solar surface at any given time.

Humankind is always fixating on the Moon and Mars as the most likely spots for the first space colonies, but there is another crazy possibility.  Aside from the Sun and the Moon, Venus is the brightest object in the night sky.  Earth’s closest planetary neighbor, Venus is a veritable sister planet with extremely similar mass and volume.  Because of its  size and position in the solar system, a great deal of early science fiction concentrated around Venus.  Dreamers and fabulists posited that beneath its ominously uniform cloud cover was a lush tropical rainforest filled with lizard people and pulchritudinous scantily clad women (the fact that the planet’s Greco-Roman name is synonymous with the goddess of love and beauty seems to have influenced many generations of male space enthusiasts).

Maybe we should head over there and check it out…

Alas, the space age quickly dispensed with mankind’s sweaty-palmed fantasies about life on Venus.  In 1970 the Soviet space probe, Venera 7, was the first spacecraft to successfully land on another planet (after a long series of earlier space probes were melted or crushed by atmospheric pressure).  In the 23 minute window before the probe’s instruments failed, the craft recorded hellish extremes of temperature and pressure. The temperature on Venus’ surface averages around 500 °C (932 °F), (higher than the melting point of lead) and the pressure on the ground is equal to the pressure beneath a kilometer of earth’s ocean.  The planet’s surface is a gloomy desertlike shell of slabs interspersed with weird volcanic features not found elsewhere in the solar system (which have strange names like “farra”,” novae”, and “arachnoids”). Additionally the broiling surface is scarred by huge impact craters, and intersected by immense volcanic mountains (the tallest of which looms 2 kilometers above Everest). The tops of these mountains are covered with a metallic snow made of elemental tellurium or lead sulfide (probably).

A photo of the surface of Venus from Venera 13

The atmosphere of Venus is a hellish fug of carbon dioxide which traps the sun’s energy in a self replicating greenhouse gone wrong.    Above the dense clouds of CO2, the upper atmosphere is dominated by sulfur dioxide and corrosive sulfuric acid.  Once Venus may have had water oceans and more earth-like conditions, but rampant greenhouse heating caused a feedback loop which caused the planet to become superheated billions of years ago.  Without an magnetosphere, solar winds stripped Venus of its molecular hydrogen (yikes!).

Artist’s Impression of the Surface of Venus

Thus Venus does not initially present a very appealing picture for colonization! Yet the planet’s mass is similar to Earth (and humans’ long term viability in low gravity is far from certain).  The planet is closer than Mars and windows of opportunity for travel are more frequent. Fifty kilometers (30 miles) above the surface of Venus, the temperature is stable between 0 and 50 degrees Celsius (32 to 122 degrees Fahrenheit).  Light crafts filled with oxygen and nitrogen would float above the dense carbon dioxide.  Today’s visionaries and dreamers therefore have stopped thinking of tropical jungles and envision instead a world of Aerostats and floating cities.  Although the rotation of Venus is too slow to craft a space elevator, the flying colonists of Venus probably could build some sort of skyhook with existing or near future technology.  Such a hook could be used to lift raw materials from the surface to manufacturing facilities in the skies.  As more aerostat habitats were built, the colony would gain manufacturing strength, safety, and a greater ability to alter the barren world below (increasingly overshadowed by flying cities and hovering countries).

Imagine then a world like that of the Jetsons where the surface was unseen and not thought about (except by scientists and industrialists).  Floating forests and croplands could be assembled to mimic earth habitats and provide resources for a bourgeoning population of Venusian humans.  Skyships would cruise between the flying city states dotted jewel-like in the glowing heavens.   Over time these flying habitats could be used to alter the planetary temperature and shield the desolate lands below.  Humankind and whatever friends and stowaways came with us would finally have a second home in easy shouting distance of Earth.    How long would it be then before we took steps to take Earth life even farther into the universe?

Ye Olde Ferrebeekeeper Archives

August 2020