Comatose on Rosetta’s comet, a follow-up on Philae

The likely position of Philae in a visualization of a topographic modeling of the comet’s surface. Credit: ESA/Rosetta/Philae/CNES/FD

As the good folks behind the Rosetta mission take a well-deserved year-end break this week and next, it’s a good time to check in on Philae, the little lander that that finally settled down for good on Comet 67P/Churyumov-Gerasimenko after bouncing three times on that gravity-deprived world.

Philae’s view of “Perihelion Cliff” at its final resting place on the comet’s surface. Reprocessing brings out more detail in rocks. The two bright spots above and below center are reflections from the metal surfaces of the spacecraft. Philae landed in a shadowed area of the comet where its solar panels can’t presently get enough sunshine to recharge the probe’s batteries. Without power, it’s now in hibernation. Credit: ESA/Rosetta/Philae/CIVA

No one yet knows exactly where the craft has landed, but using the few images taken by Philae before its batteries went dead, mission control specialists have constructed the visual (above) showing the lander tucked into a little valley alongside a steep cliff. Scientists still hope to re-activate the lander by February or March when the comet’s position relative to the Sun will allow sunlight to once again strike its solar panels and recharge the batteries.

Philae’s blurred first photo taken after its first bounce off the comet’s surface on November 12, 2014. Credit: ESA/Rosetta/Philae/CIVA

The original landing site for Philae would have been perfect for science studies up until about February or March, but too hot for the lander as the comet approached its August perihelion. Its more sheltered location fortuitously shields it from sunlight long enough to allow Philae to study the comet around and after perihelion – the reason the big rock or cliff about 3 feet away is dubbed Perihelion Cliff.

Same simulation as above showing Philae’s location but this version has the photo of Perihelion Cliff superimposed to better show where on the cliff the photo was taken. The cliff is composed of blocky, fractured ice. Credit: ESA/Rosetta/Philae/CNES/FD

The atmosphere of the comet contains a great variety of molecules, while the majority of the surface layer away from the active regions holds between 5 and 7 percent organic material.

Rosetta’s instruments have already detected a rich assortment of molecules in the hazy, temporary atmosphere of the comet called the coma. Credit: ESA

The flatter plains appear to be covered in an ice-free layer of dust and gravel about half-an-inch (1 cm) made up of low iron minerals, silicates, organics and carbon. The deeper you go, the icier it gets with a mix of dust, ice and organic materials about 4-8 inches (10-20 cm) thick. Water amounts in the coma vary according to time of day and position of the comet. Carbon dioxide emission are more constant throughout. Significant amounts of sulfur have also been found.

Who’d a- thunk it? Mercury May Have Meteor Showers Too

Artist’s concept of Mercury crossing the debris trail of Comet Encke, sparking a recurring meteor shower. New evidence from the MESSENGER mission suggests the planet receives regular doses of Mercurial dust. Credit: NASA’s Goddard Space Flight Center

Of course, of course, it only makes sense. We’re so caught up in watching meteor showers on our own planet, who ever thinks about meteors at Mercury? Or Venus for that matter? This week NASA announced that regular spikes in the amount of calcium in Mercury’s upper atmosphere bespeak a cyclical source. The likely culprit? Comet 2P/Encke.

Like breadcrumbs dropped to mark a path, dust and fragile bits of rock are released through vaporization of a comet’s ice and pushed back by the pressure of sunlight to form a tail. The larger pieces are left behind to fan out along the comet’s orbit. If by good fortune Earth’s orbit happens to intersect the debris trail, we see a shower of meteors in the sky.

This photo, made by NASA’s Spitzer Space Telescope in infrared light, shows Comet Encke’s glowing nucleus/nuclear region and a trail of warm dust and pebbly debris shed by the comet along its orbital path. Credit: NASA

Most recently, the Geminids put on a great show, although their origin lies with the peculiar rock-shedding asteroid 3200 Phaethon.

Comet 109P/Swift-Tuttle brings us the familiar Perseid meteor shower, while 2P/Encke gives rise to several meteor streams - the Southern and Northern Taurids, showers that peak in October and November, and the daytime Beta Taurids in June and July.

Measurements taken by MESSENGER’s Mercury Atmospheric and Surface Composition Spectrometer have revealed seasonal surges of calcium that occurred regularly over the first nine Mercury years (1 year = 88 Earth days) since MESSENGER began orbiting the planet in March 2011. Just as we saw huge spikes in the amounts of metals like magnesium and iron in Mars’ upper atmosphere during Comet’s Siding Spring’s brush with the planet last October, MESSENGER’s instrument detected periodic spikes in the amount of calcium – although with a twist.

A color- enhanced view of Mercury, assembled from images taken at various wavelengths by the cameras on board the MESSENGER spacecraft, shows a cratered composed with a surface composed of a variety of minerals. The circular, orange area near the center-top of the disk is the enormous Caloris impact basin. Credit: NASA / Johns Hopkins University Applied Physics Laboratory / Carnegie Institution of Washington

Mercury’s has only a whiff of an atmosphere, what astronomers term an exosphere, the last thing you could call an atmosphere before encountering the vacuum of space. The shower of small dust particles peppering interplanetary space pass right down to the surface and strike the planet’s rocks, knocking calcium-bearing molecules free from the surface, which are then free to rise to greater heights. This process, called impact vaporization, continually renews the gases in Mercury’s exosphere as interplanetary dust and meteoroids rain down on the planet.

These type of impacts happen all the time, but scientists noticed a pattern in the calcium spikes that pointed to a repeating source. Sounds like a perfect time for a comet to step in. Examination of the handful of comets in orbits that would permit their debris to cross Mercury’s orbit indicated that the likely source of the spikes was Encke.

The Jupiter family of comets were all once long-period objects in the Kuiper the orbits of which were changed to short-period by close passes by Jupiter. The green circle is Jupiter’s orbit, the purple is Earth’s. Notice that when farthest from the Sun, the comets about as far as Jupiter is from the Sun. Credit: Wikipedia with additions by the author

“If our scenario is correct, Mercury is a giant dust collector,” said Joseph Hahn, a planetary dynamist in the Austin, Texas, office of the Space Science Institute and coauthor of the study. “The planet is under steady siege from interplanetary dust and then regularly passes through this other dust storm, which we think is from comet Encke.”

To test their hypothesis, Han and crew created detailed computer simulations and discovered that the MESSENGER were offset from the expected results but in a way that made sense due to changes in Encke’s orbit over time from the gravitational pull of Jupiter and other planets.

Pantheon Fossae – The striking troughs of Mercury’s Pantheon Fossae, the feature that MESSENGER scientists first called “The Spider” when they discovered it. Credit: NASA / Johns Hopkins University Applied Physics Laboratory / Carnegie Institution of Washington

Comets get nudged by planets routinely, especially if they pass near Jupiter, the outer Solar System’s gravitational goliath. Jupiter, with the help of Neptune, has re-worked the orbits of countless bodies that once resided in the distant Kuiper Belt into shorter-period comets that swing around the Sun in 20 years or less. Called the Jupiter-family, there are about 400 known and Encke is one of them with an orbital period of just 3.3 years.

Who knows how many other meteor showers might pepper Mercury in a year, but scientists will be looking for potential signs of them in planet’s atmosphere in the months ahead. While they may not leave bold streaks of light as they do on Earth, they create something almost as amazing – a shower of particles that goes up instead of down.

Rosetta’s comet – colorful personality but gray as a foggy day

A color photo of Comet 67P/Churyumov-Gerasimenko composed of three images taken by Rosetta’s scientific imaging system OSIRIS in the red, green and blue filters. The images were taken on August 6, 2014 from a distance of 75 miles (120 km) from the comet. Click to enlarge. Credti: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Is this really a color photo? Yes! And it shows how remarkably gray and colorless the comet truly is. This is just how you’d see 67P/C-G if you could piggyback on Rosetta and whirl around it for a few orbits.

“As it turns out, 67P/C-G looks dark grey, in reality almost as black as coal,” says the instrument’s Principal Investigator Holger Sierks from the Max Planck Institute for Solar System Research.

Pictures of Enceladus, the Earth, the Moon, and Comet 67P/C-G showing their relative brightness. Saturn’s icy moon Enceladus reflects back nearly 100% of the sunlight it receives, Earth, 31% , the moon, 12% and 5% for 67P/C-G. Images not to scale. Credit: NASA/JPL/Space Science Institute (Enceladus); ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/ UPM/DASP/IDA and Gordan Ugarkovich (Earth); Robert Vanderbei, Princeton University (Moon); ESA/Rosetta/NAVCAM (67P/C-G).

The intensity of the images has been enhanced to span the full range from black to white and bring out surface details, but the colors haven’t been altered. Shadows are deep black because there’s no atmosphere to significantly diffuse the light as on Earth. Some photos however do show shadow detail from sunlight reflecting off other parts of the comet and into shadowed regions.

The comet – at least at this distance – is nothing more than a hundred shades of gray. A careful analysis shows a small amount of excess red light reflected from 67P due to fine-grained dust on its surface. We can’t see this hint of rouge because our eyes are much more sensitive to the greens, yellows and blues of sunlight, but a camera recording light reflected from the comet through multiple color filters can.

Before Rosetta moved in close to 67P/C-G, Earth-based telescopes had also shown the comet’s gray nature, but I think it’s safe to say scientists were surprised that even close-up, the comet remains a monotonous monochrome megalith.

For instance, any ice on the surface should appear brighter in the blue filter, leading to the appearance of blue-ish patches. This photo contains no indication of any such icy patches, consistent with observations made by some of Rosetta’s instruments.

So what’s up? The same thing that dulls the shine on your computer monitor coats the surface the comet: dust. Dark dust is everywhere and mission scientists are in the process of determining what it’s made of. Ice is surely there – Philae detected ice at its landing site and Rosetta’s MIRO instrument found the comet shedding 2 cups of water a second as icy vapor.

Jets of carbon dioxide blast from beneath the surface of Comet Hartley 2 in this photo taken during the flyby by NASA’s EPOXI/Deep Impact spacecraft in 2010. The jets carry water ice in the form of large snowballs (white dots) and dust particles. Credit: NASA

It would seem logical to assume that some of the dust embedded in that vaporizing ice drifts back down to the surface, quickly covering any exposed material. I’ve seen something similar happen during a winter here in Duluth, Minnesota. Grit and sand accumulate atop fresh snow. Over time, the snow compacts, melts and refreezes to form ice covered by black gunk.

Often, water escapes as a plume of dust-laden vapor through a vent in its surface like a geyser. I’d love to see a close-up of one of those. Imagine the amount and ubiquity of fine dust deposited over millions of years every time the comet swings by the Sun and gets cooked.

If we just get somebody up there to sweep the floor.

Ho-ho-ho! Comet Lovejoy Q2 brings Christmas joy

Comet Lovejoy Q2 on December 12th shows a big glowing coma and faint, 2° long gas tail. The comet becomes an easy binocular object this week for northern skywatchers. Credit: Rolando Ligustri

A naked eye comet for Christmas? Yes, Bobby there is a Santa Claus. Comet C/2014 Q2 Lovejoy, which has been slowly pushing into northern skies this month, has brightened in recent days to magnitude +6.5. That’s the cusp of naked eye visibility. A few observers in Australia, where Lovejoy hovers nearly overhead, reported seeing it faintly with the naked eye last night.

Most of us will view Q2 with ease in binoculars, especially once it gains a bit more elevation at night. Right now, the comet’s in Puppis the Stern, a gangly constellation south of the more familiar Canis Major the Greater Dog, home to Sirius, the brightest star. When best placed for observing around 1-1:30 a.m. local time it climbs to an altitude of 10° (one fist held at arm’s length) for observers in the central U.S. but just 3-5° for the northern states.

Comet Lovejoy Q2 begins its northward trek slowly but picks up speed with each passing night. On the night of December 28-29, the comet will pass 1/3° from the bright globular cluster M79 in Lepus. This map shows the sky and comet’s position facing south from 42° north latitude around 1:30 a.m. CST. Click to enlarge. Source: Chris Marriott’s SkyMap software

That will change soon as Lovejoy swings rapidly northward and rises earlier and earlier in the coming nights. By Christmas, the comet will be even brighter and stand 20° high from places like Kansas City, Denver and Indianapolis shortly before midnight.

Lovejoy Q2 is Australian amateur astronomer Terry Lovejoy’s fifth find. He snagged it while making a photographic search for comets with his 8-inch (20-cm) last August. Q2′s been on a beeline toward the Sun since that time and brightened from a 15th magnitude smudge to a robust, glowing ball with a skinny-necktie tail.

Comet Lovejoy Q2 is a long-period comet, dropping in toward the Sun with an orbital period of about 11,500 years. Here it’s shown when nearest Earth and brightest in early January 2015. The comet follows a steeply tilted orbit that takes it high over the plane of the planets. Credit: NASA/JPL HORIZONS

As it approaches Earth this month and next, Q2′s expected to brighten to 5th magnitude, putting it within naked eye range from the outer ‘burbs of a mid-sized city. Binoculars will provide a clear view of the fat, fuzzy coma and telescopes will add a faint ion tail composed of vaporizing gases fluorescing in solar UV. Cool!

Closest approach to Earth happens on January 7-8th when Lovejoy will be 43.6 million miles (70.2 million km) away. A little more than 3 weeks later on January 30, the comet passes perihelion to the Sun at a distance of 120 million miles.

I’ve included three maps to find and track Comet Lovejoy through early January. The first (top) is a wide view showing the “big picture” to help you get oriented. The others go in tighter and show black stars against a white background. I prefer them for a couple reasons – they use far less ink when making printouts and are cleaner and easier to read at the telescope. Click each to download a larger version.

Detailed map showing the comet night-by-night path starting tomorrow December 14th through December 27th in the early morning hours (CST). Stars shown to magnitude +8.0. Source: Chris Marriott’s SkyMap software

Because Comet Lovejoy moves rapidly into the evening sky by mid-late December, its position on this map is shown for 10 p.m. (CST) nightly. Mark your calendars for the close approach to M79 on Dec. 28-29. Source: Chris Marriott’s SkyMap software

I’m hoping we get out from under our week-long battle with clouds, so I can see the comet for myself. I’ll be updating all along and would love to include your observations in future blogs.

Was the water in your tea delivered by an asteroid?

Water vapor and dust jet into space from Rosetta’s comet, 67P/Churyumov-Gerasimenko in this photo taken on November 20th. Could Earth’s water have been delivered by comets impacts billions of years ago? Credit: ESA/Rosetta/Navcam

Water, water everywhere but no one’s sure how it all got here. When Earth formed 4.6 billion years ago it was incredibly hot from gravitational contraction and continuous meteorite and asteroid bombardment. Any of the planet’s original water should have boiled away into space.

To replace what went missing, it’s widely thought that water was delivered by a fusillade of asteroids and comets after Earth’s had cooled down enough for water to pool on its surface. The question has always been which was the main contributor: asteroids, composed of mostly rock, or comets, made mostly of ice. At first blush, comets seem the logical choice. Melt ice and you get water. But it’s not that simple. New data from Rosetta’s comet may point otherwise.

The normal hydrogen atom is a very simple thing – just one proton for a nucleus surrounded by one electron. Deuterium adds another proton to make “heavy hydrogen”. When two heavy hydrogen atoms join with an oxygen atom, they make heavy water. Credit: ESA

Water’s made of two hydrogen atoms bonded to one oxygen. Together they make H2O. The key to determining where the water originated is in its ‘flavor’, in this case the proportion of deuterium – a form of hydrogen with an additional neutron – to normal hydrogen in water. Because that extra neutron makes a deuterium-based water molecule heavier, it’s often referred to as “heavy water”.

Heavy water comprise just 0.2% of all naturally occurring water on Earth. Ice cubes made of it sink in a glass of ordinary water.

Illustration showing the two main reservoirs of comets –  the Kuiper Belt, which begins beyond the planet Neptune, and the Oort Cloud, which may extend up to 50 000–100 000 times Earth’s distance from the Sun. Halley’s comet is thought to originate from the Oort Cloud, while Rosetta’s Comet hails from the Kuiper Belt. It orbits the Sun every 6.5 years. Credit: ESA

The proportion of heavy vs. normal water is an important indicator of the formation and early evolution of the solar system, with simulations showing that it should change with distance from the Sun. This makes it a key diagnostic to determining where an object originated.

The proportion of deuterium to hydrogen (D/H) across the solar system as directly measured by spacecraft (diamond symbols) and by astronomical methods (circles). The horizontal bar is Earth’s D/H ratio. Notice how the asteroids prove a much better fit to Earth’s water than most comets studied to date. Rosetta’s comet (67P/C-G) is circled at right. It’s water is not related to Earth’s – a recent finding. Credit: ESA

Of the 11 comets for which measurements of deuterium to hydrogen (D/H ratio) have been made, only Comet 103P/Hartley 2 was found to match the composition of Earth’s water, in observations made by ESA’s Herschel Space Observatory in 2011. The real surprise are the asteroids. Despite generally being poor in water except for the carbon-rich carbonaceous variety, the rocky asteroids may very well have delivered much of our planet’s water after its hot-headed birth.

A slice of the Allende meteorite, that fell to Earth in 1969. Allende is a carbonaceous chondrite that originated on an asteroid that once contained water. Water delivered by way of asteroids appears a likely way for our planet to have re-stocked its supply after most of the planet’s original water boiled into space. Credit: Matteo Chinellato

“Our finding also rules out the idea that Jupiter-family comets contain solely Earth ocean-like water, and adds weight to models that place more emphasis on asteroids as the main delivery mechanism for Earth’s oceans,” said Kathrin Altwegg, principal investigator for ROSINA (Rosetta’s comet atmosphere analyzer) and lead author of the paper reporting the results in the journal Science this week.

Water in asteroids appears to be the best match for water on Earth.

So despite the fact that asteroids have a much lower overall water content, impacts by a large number of them could still have resulted in Earth’s oceans.

Wonderful, isn’t it, that the answers to some of the simplest but most profound questions are sometimes found right over our heads.

And yet. And yet I can’t help think that at least a portion of our water came right out of the ground. There’s no question that volcanoes were active on Mars 1-2 billiion  years ago; Earth must have been belching out gases and vapor at least that early or perhaps even earlier. Since the most common gas vented from volcanoes is water vapor followed by carbon dioxide it would seem we should also consider water supplied from deep magma sources that fed early volcanoes.

Not only did volcanic activity build Earth’s early atmosphere but it could have also provided a healthy dose of earthy H2O. Just a thought.

Did Jupiter deport 8 billion asteroids to the Oort Cloud?

1996 PW has a highly elongated orbit  just like a comet from the Oort Cloud – except it’s an asteroid. Astronomers now think they know how it got there. 1996 PW is about 5-10 miles (8-16 km) across. Credit: NASA/JPL-Horizons

Our view of the solar system will forever be incomplete. While frustrating at first blush, it means that fresh discoveries are always just around the corner. Case in point. On August 9, 1996 astronomers atop Mt. Haleakala in Maui, Hawaii discovered a most peculiar asteroid. 1996 PW has a highly elongated that looks like a Frisbee seen from the side and takes 5,900 years to make one trip around the Sun.

When farthest, 1996 PW is 48.8 billion miles away or 104 times more distant than Pluto. That places it among the billions of icy comets that comprise the Oort Cloud, a roughly spherical cocoon centered on the Sun and extending up to a light year from it in all directions.

Like moths around the solar flame, some 500 billion comets and perhaps 8 billion asteroids occupy a vast region of space called the Oort Cloud. The Kuiper Belt is a second asteroid belt that lies beyond the orbit of Neptune.

Odd thing was, 1996 PW was an asteroid – it never exhibited a fuzzy coma or tail typical of a comet and appeared spectroscopically to be made of rock. No dust or gas of any kind was detected even when the object was closest to the Sun. So what was it doing so far from home?

Some astronomers thought it may have been an active comet long ago but depleted its ices to where it’s now unrecognizable from an asteroid. Maybe.

A new study by Andrew Shannon (University of Cambridge), based on simulations of the rolling-stone-ways of the giant planets early in the solar system’s history, points to 1996 PW once being much closer to the Sun.

The planets haven’t always been in their present day orbits. In particular, Jupiter, the largest and most gravitationally potent planet, roamed inward to the orbit of Mars before backing out to its present orbit. Gravitational interactions with the dusty disk of material around the Sun called the solar nebula pulled the planet in. Later, interaction with Saturn yanked it back out. Scientists dub the back-and-forth shimmy the “Grand Tack”.

Interaction between the dusty-gassy solar nebula surrounding the Sun the young solar system and Saturn caused Jupiter to migrate first inward and then outward, scattering the hapless asteroids as it came and went. Credit: NASA

“We refer to Jupiter’s path as the Grand Tack, because the big theme in this work is Jupiter migrating toward the sun and then stopping, turning around, and migrating back outward,” writes Kevin Walsh of the Southwest Research Institute in Boulder, Colorado in a 2011 paper in Nature. “This change in direction is like the course that a sailboat takes when it tacks around a buoy.”

Jupiter’s gravitational might profoundly affected the asteroid belt at the time. Based on Shannon’s computer simulations, the giant planet’s do-si-do created chaos, with some asteroids kicked toward the Sun, others moved to a newly-created main belt and still others booted right out of the solar system.

Many were also flung to the icy realm of the Oort just short of leaving the Sun’s domain altogether. Shannon estimates that 4% or 8 billion rocky asteroids that once orbited within 2.5 times Earth’s distance from the Sun now mingle among the cloud’s half-trillion comets. Heck, that’s more asteroids than populate the main asteroid belt!

Very few “Oort asteroids” have been discovered and you can guess why. They’re small, generally dark and incredibly far away. A comet gives itself away with a bright coma and tail. Not these guys.They’re lurkers. To find them we’ll need dedicated, large telescope surveys like the upcoming Large Synoptic Survey Telescope with its 8-meter mirror slated for “first light” in 2019. But even that great eye will be challenged – Shannon predicts only a dozen discoveries a decade with the wide-field survey telescope.

One interesting sidelight about Oort Cloud asteroids. Like comets, they do drop in on the inner solar system from time to time. 1996 PW comes within just 232 million miles (373 million km) of the Sun. If one ever did have Earth in its sights, it would be hard to spot in advance and more difficult to divert because its much faster speed. One the bright side, Shannon and team estimate an impact would occur only once every billion years. I guess I can handle those odds and drag myself to work another day.

Rosetta captures spectacular photos of Philae drifting above comet

These incredible images show the  Philae lander’s journey as it approached and then rebounded from its first touchdown. You can even see the landing pad impressions (top inset). Pictures taken by the Rosetta OSIRIS camera 9.6 miles (15.5 km) from the surface. Click to enlarge. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Just amazing! And a little sad, too. It’s Philae coming in for its first landing attempt on comet 67P/Churyumov-Gerasimenko. You’ll recall the lander touched down without the use of its reverse thruster or the harpoons to fix it to the surface. Given the near zero-G gravity at the comet, Philae immediately rebounded to the tune of 1 kilometer (0.6 miles) and set off on a brand new path high above the comet. Rosetta was there to see it happen.

Close-up of the first touchdown site before Philae landed (left) and after clearly shows the impressions of its three footpads in the comet’s dusty soil. Times are CST. Philae’s 3.3 feet (1-m) across. Credit: ESA et. all

Rosetta captured Philae’s descent (from left to right) to the comet, the first touchdown point (top inset) and subsequent rebound and drifting off to the right or east. The craft was moving only at a walking pace (1.6 feet/sec) at the time of first contact with the comet. According to the Rosetta blog:

“The mosaic comprises a series of images captured by Rosetta’s OSIRIS camera over a 30 minute period spanning the first touchdown. The time of each of image is marked on the corresponding insets and is in Greenwich Mean Time. A comparison of the touchdown area shortly before and after first contact with the surface is also provided.”

The Rosetta spacecraft spotted Philae and its shadow shortly after the lander touched down and stirred up some dust (dark spot in larger red circle) at 9:30 a.m. (CST). The Philae image was shot five minutes later. Credit: SA/Rosetta/NAVCAM; pre-processed by Mikel Canania

We still don’t know exactly where the lander is, but after two bounces, it finally settled down for good at 11:32 a.m. (CST) a considerable distance east of the original landing site. Expect photos soon of Philae. Mission controllers are hard at work combining the CONSERT ranging data with OSIRIS high resolution and navigation camera images from the orbiter along with photos from Philae’s ROLIS and CIVA cameras to reveal to lander’s location.

Note: The two identical times in the top inset photos are correct even though they both show the same time. When the 15:43 picture was taken, Philae had moved on, but the impressions of its footpads remained.

Philae performs handstand on comet, sends back first panorama

The first panoramic image from the surface of a comet taken by the lander Philae. It’s a 360º view around the point of final touchdown. The three feet of Philae’s landing gear can be seen in some of the frames. Credit: ESA/Rosetta/Philae/CIVA

Beware small comets! Their lack of gravity can make landing hell. The Philae lander finally did settle down on comet 67P/Churyumov-Gerasimenko, but only after two tries. It attempted to touch down just a few hundred feet from the original planned site but with harpoons and rocket thrusters that failed to fire, there was no way for the probe to anchor itself. Instead it dropped to the surface and bounced straight back up into space a full kilometer (0.6 miles) above the comet.

Philae is superimposed on top of the panoramic image. The lander team believes it’s tipped up on its side. Credit: ESA

There it hovered for two hours until dropping down again and rebounding again about 1.5 inches (3 cm) high. In the incredibly low gravity field of the comet, Philae hovered for seven minutes! Then it finally came to rest tipped up on its side in a “handstand” position with one of its legs sticking straight up into outer space.

Stephan Ulamec, Philae Lander manager, describes where the craft landed in a press briefing today. It first touched down in the small red square at left, but then bounced off the comet and settled over two hours later somewhere inside the blue diamond. Credit: ESA

Scientists still hope to figure out a way to right the lander. As you try to make sense of the panorama, keep that in mind. In spite of its awkward stance, Philae’s still able to do a surprising amount of good science. But trouble looms. The craft landed in the shadow of a cliff, blocking sunlight to its solar panels which are used to charge its battery. Philae has one day of full power, which means tomorrow’s a critical day. If the battery runs too low, the probe will go into hibernation mode. The lander team are going to try and nudge Philae into the sunlight by operating the moving instrument called MUPUS tonight.

Philae is that little blip as photographed by Rosetta during the craft’s descent to the comet yesterday. Credit: ESA

Let’s wrap it up with a musical tribute to Rosetta and its mission. Somehow this comet landing, a major achievement despite its minor flaws, deserves a tribute in sound.

Rosetta’s Waltz by Vangelis


We’re on the comet, baby! Philae scores a touchdown

Rosetta team members, including  Flight Director Andrea Accomazzo (left), react to the first signal received from the Philae lander after its successful touchdown on Comet Churyumov-Gerasimenko earlier this morning. Credit: ESA

Around 9:37 a.m. (CST) Philae successfully landed on craggy comet Churyumov-Gerasimenko. The first signal, a voice from another world, arrived at 10:05. While the lander reached the surface in good health and continues to send telemetry, a small problem cropped up. The two harpoons that would anchor the craft to the comet failed to fire.

Check out this James Bond-style Swiss Army knife of a lander. Each instrument includes a short description. To read clearly, click for a large version. Credit: ESA

Right now, mission control is considering whether to re-fire them as well as figure out why they didn’t fire in the first place. In the comet’s low gravity, it’s important that Philae be sitting stably. Just think what would happen if a nearby jet erupted or ice began to vaporize around or under the craft? Weighing only a gram, Philae might easily tip over.

Here we come! The photo was taken by Philae at 8:38 a.m. (CST) when it was just 1.8 miles (3 km) above the comet. Credit: ESA/ESA/Rosetta/Philae/ROLIS/DLR

Hopefully we’ll see that first panoramic landscape photo soon. In the meantime, scientists held a press conference this afternoon to share first results as well as some of the troubles the lander faces.

Although Philae landed right on target and is gathering scientific data at this very moment, there have been problems with the radio link. Communications drop in and out for some as-yet unexplained reason. We know that neither the top rocket thruster (used to push the probe to the surface) nor the harpoons fired to anchor the craft to the comet’s surface. The data even seem to indicate that the lander may have even lifted off the ground and landed again:

Just to give you a flavor for the rugged landscape Philae was headed toward earlier today, this photo was taken by Rosetta at an altitude of 4.8 miles (7.7 km) from the comet’s surface. Credit: ESA

“Maybe today we didn’t just land once. We landed twice!” said Stephan Ulamec, Philae Lander Manager. Much is still preliminary, which is why the agency’s scientists are hard at work on the problem. Another live webcast is scheduled tomorrow at 7 a.m. (CST).

Live updates can be had on Twitter and the Rosetta website.

Philae descends to the comet, landing expected soon

The “farewell photo” taken by the Philae lander as it departed Rosetta around 2:30 a.m. (CST) today. It shows the one of the solar arrays on the spacecraft. Credit: ESA/Rosetta/Philae/CIVA

So far, so good. The European Space Agency’s Philae lander, a box of science instruments the size of a dishwasher, is now free-floating to the surface of Comet Churyumov-Gerasimenko and expected to touch down shortly. Lots more updates coming! Be sure to also check the mission’s Twitter feed.

The lander with its legs popped open photographed during its descent to the comet by Rosetta. Credit: ESA/Rosetta/MPS for Rosetta Team