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Cassini Death.jpg

This Friday September 15th is the final day of the astounding Cassini mission. The robotic space probe just took a final picture of Titan (which was arguably the site of the mission’s most breathtaking discoveries) and now the little spacecraft turns towards Saturn’s north pole and the grand finale…a plunge into the crushing atmosphere of the gas giant planet. A joint effort between NASA and the Italian space agency, Cassini launched in 1997 (the year I came to New York) and for 20 years it has sailed the solar system. In 2004, the craft reached Saturn and it has been discovering moons, taking pictures, and otherwise exploring the system ever since. Cassini even launched a lander to the surface of Titan, a super moon with a thick atmosphere and methane oceans.
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All good things must end though, and Cassini is out of fuel. Mission scientists did not wish to leave the craft orbiting for thousands of years and they also hoped to get a last trove of data (and jolt of publicity) from the mission…so the controllers opted to fly Cassini straight into the planet to learn whatever they can before the minivan sized probe blows apart and/or is crushed. Sadly there is no camera to record this melodramatic demise (which the denizens of Earth will want to see) so I have created my own rendition of the craft’s final descent using the magic of art (image at top). Since Saturn does not have an oxidizing atmosphere (probably?) and Cassini does not talk (probably?) I took a few artistic liberties, however I think I got the great hexagonal storm on the gas giant pretty well and I also captured some of the endearing personality of an astonishing robot explorer which will be dearly missed.
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Cassini-2

Seven hundred million miles away the Cassini spacecraft is preparing for death this coming September (2017). Launched in 1997 (when I moved to Brooklyn) the joint Italian/American space exploration mission to Saturn has seen and done things beyond comprehension. Lifted out of Earth’s gravity well by means of a Titan IVB/Centaur It flew through the nothingness and slingshotted around Venus (twice), the Earth, and Jupiter. It discovered new oceans on Enceladus and launched a lander onto the supermoon Titan (the first ever landing in the outer solar system). Cassini was used to tested general relativity: the craft broadcast radio past the sun to the Earth so that scientists could measure how the star’s gravity distorted the electromagnetic waves. Powered only by pluck (and, uh, 33 kilograms of plutonium-238) the little probe visited 20 moons.
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But all good things come to an end, and this final phase may be the most dramatic. On April 26th the craft began weaving between Saturn’s rings and the top of the planet’s atmosphere. The image at the top is an artist’s conception of how this might look for Cassini. The second image is a picture of the enormous hexagonal storm at the north pole taken April 30th. The image below is an infrared picture of Saturn. Cassini is scheduled to make 20 more of these passes before its final fiery plunge into Saturn itself, so prepare for more mind-boggling images of the gas giant.
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Artist's conception of Venus Express above Venus (ESA)

Artist’s conception of Venus Express above Venus (ESA)

Tomorrow I will write the obligatory annual post about whom we lost in 2014.  It’s always a solemn occasion which highlights the passing of many eminent figures (as well as the passing of yet another year) and raises troubling questions about what is truly important.  But before we get to the human obituaries, I wanted to write a quick eulogy for an underappreciated figure lost to little fanfare at the end of 2014.  Last month the robot explorer craft “Venus Express” was destroyed by falling into the volatile high-pressure atmosphere of our sister planet Venus (an operatic end which overshadows all but the greatest human deeds).  The Venus Express was a satellite launched by the European Space Agency in November 2005.  It reached polar orbit around Venus in April of 2006 and has been continuously sending back data since then until November 28th of 2014 when the last remaining fuel in the satellite was used to lift it into a high orbit.  Scientists planned on monitoring the space probe during its long drift down to the top of the atmosphere, but something went wrong and the satellite was thrown into a spin (which made it unable to contact Earth).  It is now presumed destroyed.

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Venus Express was the first Venus mission undertaken by the ESA.  Now that the craft is gone, the human race has no functional probes or spacecraft on or around Venus until the Japanese climate orbiter “AKATSUKI” is scheduled to reach there sometime in 2015 (although there have been some problems with that mission and the planned rendezvous may be postponed…or never happen).

This still from a NASA animation of a concept Venus mission shows a probe, one of many, beginning its descent into the Venus atmosphere.

This still from a NASA animation of a concept Venus mission shows a probe, one of many, beginning its descent into the Venus atmosphere.

Venus’ atmosphere is believed to have once been much like that of Earth.  This is certainly not the case now! The data from Venus Express is now being analyzed in order to ascertain what happened to transform Venus into a hellish greenhouse (and strip it of its magnetosphere).  Maybe we can also analyze this data with an eye on future sky colonies as well.  Venus Express discovered hydroxyls in the atmosphere of Venus. It also discovered an ozone layer and a high cold atmospheric layer which is possibly dry ice.  It undertook a series of aerobraking experiments which could prove very relevant to future craft inserted into Venus’ atmosphere.  We need someone to analyze this data and plan those future missions! Speaking of which, why doesn’t NASA have more exploratory missions planned to this nearest planet?  We should try to put a long-term floating probe into the upper atmosphere of Venus itself!  That would be an amazing accomplishment and it would tell us more about whether floating sky colonies above Venus would even be possible. Nothing is more alluring than Venus!  Let’s honor the Venus Express by learning from it and sending some more missions there pronto!

The Birth of Venus (Henry Courtney Selous, 1852, oil on canvas)

The Birth of Venus (Henry Courtney Selous, 1852, oil on canvas)

The Three Trees (Rembrandt Harmenszoon van Rijn, 1643, intaglio print)

The Three Trees (Rembrandt Harmenszoon van Rijn, 1643, intaglio print)

It is Rembrandt’s birthday again—happy birthday to the great artist! Last year we looked at an enigmatic painting by the great Dutch master which could have represented several different mythological/historical scenes. This year instead of celebrating with one of his astonishing paintings of people, we turn instead to an intaglio print which Rembrandt made by combining etching, drypoint, and direct hand manipulation of the printer’s ink. Uncharacteristically, humankind is not the direct subject of the print (although if you enlarge the image, you will discover both a fisherman plying his luck at the river and a yokel loitering in the fields). Three monumental trees loom over the flat Dutch landscape—but their symbolism, if any, is not overt. A bustling city sprawls in the background, but it too is not the focal point on the composition. The real subject is the darkling sky which roils with strange clouds, abstruse turbulence, and glorious patches of sunlight. The world changes with astonishing speed: the mutable clouds are the most direct manifestation of the ever shifting nature of reality, yet the country dwellers, cows, city, and even the long-lived trees all seem to partake of the same impermanence.

jcosmosWhen I was a child, my favorite tv show was Carl Sagan’s Cosmos.  Although the good doctor’s naïveté about cold war politics sometimes dismayed my realpolitik-minded parents, the amazing breadth of his show’s exploration of the natural world–and the wider universe beyond–was a wonder to me.  For the first time I was introduced to quasars, pulsars, and stellar aging. From Sagan’s delightfully filmed documentary, I learned about Kepler, the Kreb’s cycle, DNA pair sequencing, and the great library of Alexandria.  The eclectic scope of Cosmos was a direct inspiration for this blog (although I can hardly claim to be such a polymath). Hopefully the new Cosmos–with a new science hero, Neil deGrasse Tyson–will inspire today’s generation of children to look beyond sports and the internet up to the soaring science of the firmament!

Jovian Life Envisioned by Adolf Schaller for COSMOS, Carl Sagan (1980)

Jovian Life Envisioned by Adolf Schaller for COSMOS, Carl Sagan (1980)

My very favorite segment of Cosmos however, did not involve real science at all, but rather airy speculation about extraterrestrial life on a gas giant planet.  Carl Sagan, his physicist colleague, E. E. Saltpeter, and the space artist, Adolf Schaller, worked together to imagine a floating ecosystem which might exist on a planet such as Jupiter. In the tempestuous atmosphere of such a world, ammonia, hydrogen, methane, and water are violently stirred together to form organic molecules.  Small drifting organisms might feed on these compounds and reproduce as lighter spores before air currents bear them down to their doom (in a cycle reminiscent of phytoplankton). Giant floating life-forms like living hot-air balloons would stay in the habitable zone of the atmosphere by photosynthesis or by grazing on the microscopic “plankton”.  These beings could be kilometers in diameter and would congregate in vast aerial schools.  Sagan and Saltpeter even envisioned jet-propulsion super predators which would blast through the alien skies feeding on the huge clouds of “floaters”.


It is a tremendously compelling vision! Now, whenever NASA or ESA releases a new list of exoplanets, I pause to wonder whether such alien creatures are actually found floating on the super-Jupiters and strange giant worlds which orbit far-off stars.  However today I would like to present an even more fantastic vision—and one which humankind could actually create!  By combining Sagan’s imaginary vision with contemporary aerospace and biotech research, it is possible to visualize my own fantasy of human colonization of Venus…or even upon other worlds with complex atmospheres.

Ornithopter based on Jellyfish (Dr. Ristroph and Dr. Childress)

Ornithopter based on Jellyfish (Dr. Ristroph and Dr. Childress)

Just this year, two aeronautical engineers, Dr. Ristroph and Dr. Childress, crafted an ornithopter based on the swimming motion of a jellyfish.  The tiny mechanism relies on four teardrop-shaped wings oriented around a dome-like apex to achieve stable, directed flight. At the same time a new array of futuristic blimps, zeppelins and dirigibles are being brought to market to transform the skies of earth.  Most importantly Craig Ventner, the bioengineer-entrepreneur, is out there sampling the esoteric genetics of the deep ocean and forging ahead with synthetic genomics (which is to say he is building new living things from scratch).  In our lifetime someone will figure out how to meld Ventner’s synthetic organisms with the advanced engineering and technology which are the hallmark of our age.  The possibilities then grow exponentially out of this world.

“Space Zeppelin” by Rugose.

“Space Zeppelin” by Rugose.

Imagine if the floating ecosphere invented by Sagan and Saltpeter were instead a floating society-economy based on advanced engineering and bioengineering.  There would be levitating cities which are also bioengineered life-forms (like the vast balloon beings of Sagan’s invention).  Between these cloud cities would fly flocks of tiny ornithopters that would gather resources for further farming/engineering.

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Jet propelled aircrafts and super habitats would zip between the living arcologies.  Armored crawlers would inch through the deeper layers of atmosphere or creep along the molten pressurized ground. Eventually there might be flying bio-colonies which self arrange out of many highly specialized flying zooids—like the siphonophores which are so prevalent in our oceans! These collective entities would act as sky factories to build an ever more symbiotic and efficient synthetic ecosystem. Humankind, living things, and technology would no longer be at odds but would grow together to form the ideal world of tomorrow.  Life, beautiful and united would expand to new planets and develop into a stronger, brighter presence in the cosmos.

Siphonophorae (Ernst Haeckel, 1904, plate 7 of "Kunstformen der Natur")

Siphonophorae (Ernst Haeckel, 1904, plate 7 of “Kunstformen der Natur”)

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?

The surface area of Earth is about 510 million square kilometers.  That number adds some perspective to the giant storm which has been raging on Saturn since December and now covers approximately 4 billion square kilometers of the gas giant planet.

The Storm Raging on Saturn (photo from the Cassini probe, NASA)

Saturn’s atmosphere is usually calm and tranquil–although powerful storms have been observed by telescope in the past. Now however Saturn is being closely observed by NASA’s Cassini space probe which is in orbit around the planet and we have some precise details.  At the storm’s height, Cassini detected over 10 lightning strikes per second.  Additionally, these lightning bursts can emit 10,000 times the amount of electrical energy as a typical lightning burst on Earth.  Saturnian meteorologists (or whatever weather scientists for the great ringed planet are called) speculate that this super lightning is so powerful because of the juxtaposition of layers of water ice with layers of crystallized ammonia.

A Detailed False Color Picture of the Storm (NASA)

Saturn’s weather is known to fluctuate with the change of the season on the frigid planet and the huge rings are presumed to affect the weather in unknown and unpredictable ways. The current giant storm is taking place in the northern hemisphere of Saturn, which is entering spring.

Although Saturn’s storms are not as well-known as the Great Red Spot on Jupiter, the planet’s north pole does feature a hexagonal storm which has persisted for at least 25 years.  Named for Jupiter/Zeus’ father (who was known as Cronus to the Greeks), the planet Saturn is the second largest in the solar system with a surface area of 4.27 x 1010 square km.  The planet is orbited not only by its famous rings but also by at least 62 known moons including Titan, the only known satellite with a dense atmosphere, and Mimas, which features the largest known impact crater.

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