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Today we have some exciting news from out there in the solar system [checks notes] er, excuse me, I guess I mean “in there” in the solar system, since today’s news concerns from the planet closest to the sun. Yet, even though it is first, Mercury is shockingly unknown compared to the other planets of the solar system. This past Friday (October 1st 2021), the joint ESA/JAXA space mission BepiColombo (which launched back in 2018) finally made it to the innermost world. Since 2018, the transfer module has been slaloming around Earth and Venus in order to make it to Mercury. Indeed, the mission is named after the brilliant Italian astrophysicist who first proposed interplanetary gravity assist maneuvers as a mechanism for altering the velocity and trajectory of interplanetary spacecraft. BepiColombo took the picture at the top of this post, a view of part of Mercury’s northern hemisphere taken at a distance of about 2,420 kilometers (1,500 miles) from the world.
In 2025, the spacecraft will deploy two orbiters to truly comprehensively map Mercury and attempt to unlock the mysteries of the planet’s ancient face. Mercury’s surface seems to be made of a very dark lava which has been bombarded by meteorites for the last several billion years. Although Mercury is dinky in volume (smaller than some of the solar system’s moons) it is quite dense and presumably contains a metallic core suitable for a much larger planet. Interestingly (albeit unsurprisingly, for anyone who lives here) the densest planet in the solar system is Earth!
Not since the end of the Messenger mission has Mercury been the thrilling center of attention in astronomy. I can hardly wait for subsequent discoveries about the fast, hot, tiny planet. Some of the secrets of the making of the solar system have been locked away on the little world, waiting billions of years for the right orbiter to come along.
Hey, did anybody notice there is a massive spooky ghost galaxy right next door to us? Well, actually the answer turns out to be “no: not really…not until November of last year.” It was only in November of 2018 that astronomers discovered Antlia 2, a galaxy which is a mere 130,000 light-years away from the Milky Way–which really is right next door in terms of cosmic distances (to contextualize this number, the diameter of the Milky Way itself is between 150,000 and 200,000 light years).
Ant2, as it is affectionately (?) called, is closer than the Large Magellanic Cloud, a dwarf galaxy with 30 billion stars which is 163,000 light years away and is generally regarded as our closest galactic neighbor. How did we miss this thing? And why are we calling it a ghost galaxy (aside from the fact that that sounds impossibly cool)?
Antlia 2 is a weird sort of celestial object. It has the lowest “surface brightness” of any known galaxy and is approximately 100 times more diffuse than any known ultra diffuse galaxy. Gee! that is really extremely diffuse. Antlia 2 is also a dark matter galaxy: the exiguous stars of which it consists are insufficient to hold it together without a great deal of unknown mystery mass. The ghost galaxy may be more than 99 percent dark matter. Additionally, Ant2 (insomuch as it exists) is hidden by the occlusion cloud above the spiral of the Milky Way. Only with the advanced astrometry readings of the European Space Agency’s satellite observatory Gaia were astronomers finally able to pinpoint this dark shadow in the sky above the southern constellation Antlia (which itself is named after an 18th century air pump).
What the jazz? This post is making less sense than usual, but I am not making any of it up…
I worry that this post is too abstruse for comfort. It concerns an all-but-invisible phantom galaxy made of unknown dark matter. The only reason we even found it to begin with is that astronomers were on the lookout for a hidden galaxy. Some unknown mass must have caused the stylish ruffles in the spiral arms of our own bright & lively Milky Way. Thus the fashion sensibility of space topologists helped us to find Antlia 2. Remind me about this thing in October. I want to draw some ghost galaxies to celebrate Halloween this year!
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.
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.
As we proceed further into the Halloween season, a long dormant specter has unexpectedly emerged from the past to claim another victim. In the early era of space exploration a shockingly high number of Mars missions were complete failures. This led space agencies to talk about the “Galactic Ghoul” a malevolent (and wholly imaginary!) entity which devours Mars probes. Well, actually the phrase “Galactic Ghoul” was coined in the nineties…before that, this high failure rate was attributed to “the Curse of Mars” which isn’t quite as vivid a personification of failure but which still effectively evokes a malevolent supernatural thing out in the darkness between worlds. The ghoul (or curse) was particularly hard on Soviet craft and a shockingly large number of Soviet missions just vanished into the void for no reason as detailed in this dramatic chart (which is worth looking at for all sorts of reasons).
The curse even manifested in the late nineties when NASA screwed up the distinction between matric and non-metric units of measurement and fired the Mars Climate Orbiter straight into the Martian atmosphere where it disintegrated (although that seems like it could be chalked up to a different old nemesis: being bad at math). At any rate, the ghoul has been quiescent for a while as NASA learned to operate on the red planet (and triple check their numbers).
Today though brings more grim news from the Red Planet. The ESA and the Russian space agency collaborated on ExoMars a joint mission in which the two teams sent an orbiter and a lander to Mars together. The Trace Gas Orbiter is the real scientific component of the mission. It will assay Mars for methane sources (we would like to know where the atmospheric methane of Mars comes from since it should be scrubbed from the thin Martian atmosphere faster than it can build up). The lander was named for Giovanni Schiaparelli, the 19th-century Italian astronomer who popularized the idea of Martian canals (a concept long since disproven but bearing elements of truth).
Schiaparelli’s only scientific payload was a small weather station that would have run for a few days before running out of batteries. It was really a lander designed to test out Martian landing capabilities, however, as of press time, the lander had proceeded into the Martian gravity well and then went ominously and completely silent. Is the galactic ghoul now sated or will it need to feed on the next charismatic lander headed to the red planet? Elon Musk may want to do some animal sacrifice and appeasement dances before he launches his colony ship!
Last week I meant to include an elegiac post to Rosetta, an astonishing space mission, which stretched out over a dozen years and logged 4.9 billion miles of travel. Rosetta was launched way back in 2004. It was originally supposed to rendezvous with comet 46P/Wirtanen in 2011, but problems with the launch in Guyana caused the probe to miss the launch window for the primary mission. The ESA changed the mission parameters so that the spacecraft ended up exploring Comet 67P/Churyumov–Gerasimenko instead (this second comet was functionally the same as the first—except for a much more difficult-to-say name). During its journey to the comet, Rosetta also flew by Mars and two asteroids. After flying by Mars in February of 2007, the craft flew by Earth in November of 2007. It caused a miniature panic when astronomers of the Catalina sky survey spotted it and misidentified it as a 20 meter near-Earth asteroid on a possible collision path with Earth!
The spacecraft arrived at Comet 67P/Churyumov–Gerasimenko in August of 2014 and the most famous…and infamous…part of the mission took place in November of that same year, when Rosetta launched the Philae lander to harpoon itself to the comet. Although Philae (which was named after a Rosetta-like obelisk with the same text in Greek and Egyptian) succeeded in landing and not bouncing off into the void, sadly the little lander came down in a miserable crevasse. Scientists intimately studied pictures of the comet (from Rosetta) until they found the lander in the icy chaos. It was a pretty ghastly scene which reminded me of my sock drawer (if it were dropped from space onto Tungnafellsjökull glacier).
(See it there at bottom right?)
Rosetta’s long and mostly successful mission came to an end last Friday in a truly operatic fashion. Mission controllers chose to use the last vestiges of power to smash the orbiter into the comet! Well, although I am saying “smashed” what actually happened was more like a grandmother walking into a snowbank. The lander was lowered onto the comet at about one mile per hour. Except, despite the fact that Rosetta traveled more than 5 billion miles (“uphill both ways”) it was not designed for landing and its last communication was a photo just above the comet surface. RIP Rosetta, you were one good probe!
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.
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.
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)
Congratulations to the European Space Agency for successfully landing the robot probe “Philae” on comet 67P! The lander, which is about the size of a washing machine, made a soft touch-down on the comet at 3:30 a.m. Brooklyn time. The comet itself has a diameter of four kilometers (2.5 miles) meaning it is approximately as wide as the Verrazano Bridge is long. To bring such objects together as they hurtle at ridiculous speeds through the vast darkness of space is a tremendous feat of engineering. Ferrebeekeeper described the long and complex journey of Philae’s mothership, Rosetta, in this previous post.
An artist’s mock-up of how the probe might look on the comet’s surface (the underdressed astrophysicist is added for scale and is presumably not there)
Philae is equipped with space harpoons which are designed to fire into the comet’s surface–thus securing the craft to the flying iceball with lamprey-like tenacity. Actually, a lamprey might be the wrong comparison: the lander looks astonishingly like a bacteriophage (a fact which I think is exceedingly strange and funny). At any rate, it is presently unclear whether the landing harpoons correctly deployed into the comet’s surface. We’ll know more in coming days.
Indeed, in coming days we should be finding out lots of things regarding the comet. The lander has a small drill which is meant to mine 20 cm (8 inches) into the icy substrate. The sophisticated machine is also equipped with devices to analyze the core sample, gas analyzers to identify any complex organic compounds, and instruments to measure the comet’s magnetic field. Scientists will be keeping a close eye on the comet to see what effect the solar wind has on it as 67P sweeps in close to the sun in coming months.
November 13th UPDATE: It seems the plucky lander had a more adventuresome landing than yesterday’s rosy headlines may have indicated. Apparently Philae landed not once, but multiple times as it bounced down a cliff and fetched up (on two of three legs) in a shadow. Mission controllers are contemplating whether to fire the landing harpoons, but are concerned that the resultant explosion could send Philae careening off the comet into the outer dark. Anyone who has thrown a washing machine down an ice cliff in low gravity will surely sympathize with their predicament…
Artist’s Impression of the Rosetta Mission
Devoted readers have most likely been fretting and worrying about what happened to the ESA spacecraft Rosetta which Ferrebeekeeper wrote about back in January. In that article, I wrote that the spacecraft was meant to rendezvous with comet 67P/Churyumov-Gerasimenko in May—but that never happened. What’s the story? Did something go wrong?
Fortunately today’s space news is good: after a ten-year chase which has spanned back and forth across the solar system, the little spacecraft finally entered orbit around comet 67P/Churyumov-Gerasimenko. The comet and the spacecraft are currently about 405 million kilometers from Earth (which puts them between the orbits of Mars and Jupiter). It turns out that May was actually the date that pre-orbit maneuvers were first commenced—it has taken three months to bring the spacecraft into proper position for orbital insertion. I’m sorry I got your hopes up prematurely, but this is a good illustration of how delicately operations must be conducted when dealing with objects going 55,000 kilometers per hour (34,000 miles per hour).
An August 3 photograph of Comet 67P/Churyumov-Gerasimenko taken by space probe Rosettas OSIRIS from a distance of 285 km (Photo: ESA/Rosetta)
The probe has already taken some amazing pictures of the comet which has two distinct masses joined together by a narrow neck—rather like a rubber duck. We can expect even more stunning pictures of the weird icy surface of the comet as the probe edges nearer to the big dirty snowball over the next few months. The real excitement will(probably) take place in November which is when the probe Philae is tentatively scheduled to launch. Philae is a comet lander which looks curiously like a bacteriophage. It will shoot harpoons into the comet and then fasten down onto the surface to study the origins of the solar system! Get ready for a thrilling fall!
Artist’s impression of the Philae landing craft, anchored by harpoons and drills to the comet’s surface
An Artist’s Rendering of Rosetta Approaching the Comet (ESA)
Today a winter snow storm has transformed Brooklyn into a huge ice ball–at least metaphorically speaking–but the weather will surely improve. Home will not be a ball of ice forever. The same cannot be said for the Philae robotic lander which is currently aboard the European Space Agency’s Rosetta spacecraft (which, in turn, is currently in outer space returning to the inner solar system after 31 months in the dark cold outer solar system). If all goes according to plan, the Rosetta spacecraft will enter a slow orbit around comet 67P/Churyumov–Gerasimenko in May of 2014. Once the space probe is in orbit around the comet, it will (eventually) fire the Philae probe onto the comet itself. Philae is equipped with space harpoons to latch on to the comet’s surface and cling to the hurtling slushball. Once there, the little robot lander will assay the comet with its drill and ten onboard sensors in order to learn more about the birth of the solar system–when the comet (probably) came into existence.
An artist’s rendering of Philae Making a Soft Landing on the Comet this coming November (ESA)
There are many remarkable aspects to this astonishing mission (which launched a decade ago), but one of the most harrowing periods just ended. Because the spacecraft is powered by solar panels, it did not receive sufficient energy to operate during its long sojourn through the outer solar system. For two-and-a-half years, the mission controllers in Darmstadt, Germany have been in suspense waiting to see if Rosetta had survived being all but shut down (because of a last-minute mission rewrite, the craft was not designed for any such suspended animation). Yesterday the spaceship woke up and radioed back to Earth! The mission is on! I can hardly wait for May (for multiple reasons).
A Comparison of the relative sizes of the Fomalhaut system and the solar system (image created by NASA and ESA)
Fomalhaut is a star with twice the mass of the sun located approximately 25 light-years from Earth in the constellation Piscis Austrinus. It is a bright young star 100 to 300 million years old (out of a projected lifespan of 1 billion years). Coinicientally the name Fomalhaut is Arabic and means “mouth of the Southern fish.” Fomalhaut has at least one planet—Fomalhaut b, which is believed to be approximately the same size as Jupiter (but could be anywhere from the size of Neptune to 3 times as large as Jupiter). Just as Saturn is surrounded by a ring of debris, the entire star system of Fomalhaut is surrounded by a giant toroidal circumstellar disk. This torus is vastly greater in diameter than our entire solar system (including the Oort Belt) and is made up of somewhere between 260 billion and 83 trillion comets which are constantly colliding and annihilating each other! The Herschel Space Observatory recently captured an infrared image of this immense comet storm.
An infrared image of the Fomalhaut system--and its huge cloud of disintegrating comets) captured by the Herschel Space Observatory (credit: ESA)
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