Rosetta Sees Fascinating Changes in Comet 67P

A new jet issues from a fissure in the rugged, dusty surface of Rosetta's comet. Credit: ESO/Rosetta/Navcam

It only makes sense. Sunlight heats a comet and causes ice to vaporize. This leads to changes in the appearance of surface features. For instance, the Sun’s heat can gnaw away at the ice on sunward-facing cliffs, hollowing them out and eventually causing them to collapse in icy rubble. Solar heating can also warm the ice that’s beneath the surface.

When it becomes a vapor, pressure can build up, cracking the ice above and releasing sprays of gas and dust as jets. New images compared to old suggest the comet’s surface is changing as it approaches the Sun.

Take a look at this photo taken on December 9 of a part of the neck of the comet called Hapi. I've labeled a boulder and three prominent cracks. Sunlight is coming from top and behind in this image. Compare to the photo below shot on Jan. 8. Credit: ESA/Rosetta/Navcam
Take a look at this photo taken on December 9 of a part of the neck of the comet called Hapi. I’ve labeled a boulder and three prominent cracks. Sunlight is coming from top and behind in this image. Compare to the photo below shot on Jan. 8. Credit: ESA/Rosetta/Navcam

Recent photos taken by the Rosetta spacecraft reveal possible changes on the surface of 67P/Churyumov-Gerasimenko that are fascinating to see and contemplate. In a recent entry of the Rosetta blog, the writer makes mention of horseshoe-shaped features in the smooth neck region of the comet called “Hapi”. An earlier image from Jan. 8 may show subtle changes in the region compared to a more recent image from Jan. 22. We’ll get to those in a minute, but there may be examples of more vivid changes.

Although the viewing angle and lighting geometry has changed some between this photo, taken Jan. 8, and the one above, it certainly appears that the three cracks have virtually disappeared in a month's time. The same boulder is flagged in both photos. Credit: ESA/Rosetta/Navcam
Although the viewing angle and lighting geometry has changed some between this photo, taken Jan. 8, and the one above, it certainly appears that the three cracks have virtually disappeared in a month’s time. The same boulder is flagged in both photos. Credit: ESA/Rosetta/Navcam

I did some digging around and found what appears to be variations in terrain between photos of the same Hapi region on Dec. 9 and Jan.8. Just as the other writer took care to mention, viewing angle and lighting are not identical in the images. That has to be taken into account when deciding whether a change in a feature is real or due to change in lighting or perspective.

Side by side comparison of the two image from Dec. 9, 2014 (left) and Jan. 8, 2015. Credit: ESA/Rosetta/Navcam
Side by side comparison of the two image from Dec. 9, 2014 (left) and Jan. 8, 2015. Credit: ESA/Rosetta/Navcam

But take a look at those cracks in the December image that appear to be missing in January’s. The change, if real, is dramatic. If they did disappear, how? Are they buried in dust released by jets that later drifted back down to the surface?

Comparison of Jan. 22 and Jan. 9 photos of the "horseshoes" or depressions in 67P's Hapi region. Outside of differences in lighting, do you see any changes? Credit: ESA/Rosetta/Navcam
Comparison of Jan. 22 and Jan. 9 photos of the “horseshoes” or depressions in 67P’s Hapi region. Outside of differences in lighting, do you see any changes? Credit: ESA/Rosetta/Navcam

Now back to those horseshoe features. Again, the viewing angles are somewhat different, but I can’t see any notable changes in the scene. Perhaps you can. While comets are expected to change, it’s exciting when it seems to be happening right before your eyes.

Four-image mosaic shows the overall view of the comet on January 22 photographed 17.4 miles (28 km) from its center. The larger of the two lobes is at left; Hapi is the smooth region at the transition between the lobes. Credit: ESA/Rosetta/Navcam
Four-image mosaic shows the comet overall on January 22 from a distance of 17.4 miles (28 km) from its center. The larger of the two lobes is at left; Hapi is the smooth region at the transition between the lobes. Credit: ESA/Rosetta/Navcam

Latest Research Reveals a Bizarre and Vibrant Rosetta’s Comet

Dust-covered, boulder-strewn landscape on the smaller of the two lobes of Comet 67P/Churyumov-Gerasimenko taken from a distance of 5 miles (8 km). Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

We’ve subsisted for months on morsels of information coming from ESA’s mission to Comet 67P/Churyumov-Gerasimenko. Now, a series of scientific papers in journal Science offers a much more complete, if preliminary, look at Rosetta’s comet. And what a wonderful and complex world it is.

Scientists have defined 19 regions on Comet 67P/Churyumov-Gerasimenko's nucleus grouped according to terrain. Each is named for an ancient Egytptian deity. Credits: ESA/Rosetta/MPS/OSIRIS Team/UPD/LAM/IAA/SSO /INTA/UPM/DASP/IDA
Scientists have defined 19 regions on Comet 67P/Churyumov-Gerasimenko’s nucleus according to terrain and named for Egyptian deities like Imhotep, Aten and Hathor. Credits: ESA/Rosetta/MPS/OSIRIS Team/UPD/LAM/IAA/SSO /INTA/UPM/DASP/IDA

Each of the papers describes a different aspect of the comet from the size and density of dust particles jetting from the nucleus, organic materials found on its surface and the diverse geology of its bizarre landscapes. Surprises include finding no firm evidence yet of ice on the comet’s nucleus. There’s no question water and other ices compose much of 67P’s 10 billion ton mass, but much of it’s buried under a thick layer of dust.

Despite its solid appearance, 67P is highly porous with a density similar to wood or cork and orbited by a cloud of approximately 100,000 “grains” of material larger than 2 inches (5 cm) across stranded there after the comet’s previous perihelion passage. Thousands of tiny comet-lets!
Continue reading “Latest Research Reveals a Bizarre and Vibrant Rosetta’s Comet”

There’s a Crack Forming on Rosetta’s 67P. Is it Breaking Up?

A Fissure spanning over 100 meters across the neck of Rosetta's comet 67P raises the question of if or when will the comet breakup. The fissure is part of released studies by Rosetta scientists in the Journal Science (Image Credits: ESA/Rosetta, Illustration, T.Reyes)

Not all comets break up as they vent and age, but for Rosetta’s comet 67P, the Rubber Duckie comet, a crack in the neck raises concerns. Some comets may just fizzle and uniformly expel their volatiles throughout their surfaces. They may become like puffballs, shrink some but remain intact.

Comet 67P is the other extreme. The expulsion of volatile material has led to a shape and a point of no return; it is destined to break in two. Songwriter Neil Sedaka exclaimed, “Breaking Up is Hard to Do,” but for comets this may be the norm. The fissure is part of the analysis in a new set of science papers published this week.

Top left: The Hathor cliff face is to the right in this view. The aligned linear structures can be clearly seen. The smooth Hapi region is seen at the base of the Hathor cliff. Boulders are prevalent along the long axis of the Hapi region. Bottom left and right: Crack in the Hapi region. The left panel shows the crack (indicated by red arrows) extending across Hapi and beyond. The right panel shows the crack where it has left Hapi and is extending into Anuket, with Seth at the uppermost left and Hapi in the lower left. (Credit: ESA/Rosetta)
Top left: The Hathor cliff face is to the right in this view. The aligned linear structures can be clearly seen. The smooth Hapi region is seen at the base of the Hathor cliff. Boulders are prevalent along the long axis of the Hapi region. Bottom left and right: Crack in the Hapi region. The left panel shows the crack (indicated by red arrows) extending across Hapi and beyond. The right panel shows the crack where it has left Hapi and is extending into Anuket, with Seth at the uppermost left and Hapi in the lower left. (Credit: ESA/Rosetta)

The images show a fissure spanning a few hundred meters across the neck of the two lobe comet. The fissure is just one of the many incredible features on Comet 67P and is reported in research articles released in the January 22, 2015, edition of the journal Science.

What it means is not certain, but Rosetta team scientists have stated that flexing of the comet might be causing the fissure. As the comet approaches the Sun, the solar radiation is raising the temperature of the surface material. Like all materials, the comet’s will expand and contract with temperature. And diurnal (daily) changes in the tidal forces from the Sun is a factor, too.

An image sequence from the Navcam of the Rosetta spacecraft (right) is shown beside a simulation. Further work on the interaction of comets with solar radiation will include computer models that utilize Rosetta data to reveal how comet nuclei evolve over time – over many orbits of the Sun- and break up. Peanut, rubber-duck, potatoes or just round-shaped comet nuclei likely result from combinations of rotation, changes in rotation, spin rate, composition and  internal structure, as a nucleus interacts with the Sun over many orbits. (Credits: ESA/Rosetta, Illustration – J.Schmidt)

 

The crack, or fissure, could spell the beginning of the end for comet 67P/Churyumov–Gerasimenko. It is located in the neck area, in the region named Hapi, between the two lobes that make 67P appear so much like a Rubber Duck from a distance. The fissure could represent a focal point of many properties and forces at work, such as the rotation rate and axis – basically head over heels of the comet. The fissure lies in the most active area at present, and possibly the most active area overall. Though the Hapi region appears to receive nearly constant sunlight, at this time, Rosetta measurements (below) show otherwise – receiving 15% less sunlight than elsewhere.

Left: A map looking at the northern (right-hand rule, positive) pole of 67P showing the total energy received from the Sun per rotation on 6 August 2014. The base of the neck (Hapi) receives ~15% less energy than the most illuminated region, 3.5 × 106 J m-2 (per rotation). If self-heating were not included, the base of the neck would receive ~30% less total energy. Right: Similar to the left panel but showing total energy received over an entire orbital period in J m-2 (per orbit). (Credit:ESA/Journal Science Article, Figure 5)
Left: A map looking at the northern (right-hand rule, positive,) pole of 67P showing the total energy received from the Sun per rotation on 6 August 2014. The base of the neck (Hapi) receives ~15% less energy than the most illuminated region, 3.5 × 106 J m-2 (per rotation). If self-heating were not included, the base of the neck would receive ~30% less total energy. Right: Similar to the left panel but showing total energy received over an entire orbital period in J m-2 (per orbit). (Credit:ESA/Journal Science Article, Figure 5)

Sunlight and heating are major factors and the neck likely experiences the greatest mechanical stresses – internal torques – from heating or tidal forces from the sun as it rotates and approaches perihelion. Rosetta scientists are still not certain whether 67P is two bodies in contact – a contact binary – or a shape that formed from material expelled about the neck area leading to its narrowing.

Fragmentation of comets is common. Many sungrazers are broken up by thermal and tidal stresses during their perihelions. At top, an image of the comet Shoemaker-Levy 9 (May 1994) after a close approach with Jupiter which tore the comet into numerous fragments. An image taken by Andrew Catsaitis of components B and C of Comet 73P/Schwassmann–Wachmann 3 as seen together on 31 May 2006 (Credit: NASA/HST, Wikipedia, A.Catsaitis)
Fragmentation of comets is common. Many sungrazers are broken up by thermal and tidal stresses during their perihelions. At top, an image of the comet Shoemaker-Levy 9 (May 1994) after a close approach with Jupiter which tore the comet into numerous fragments. An image taken by Andrew Catsaitis of components B and C of Comet 73P/Schwassmann–Wachmann 3 as seen together on 31 May 2006 (Credit: NASA/HST, Wikipedia, A. Catsaitis)

The Philae lander’s MUPUS thermal sensor measured a temperature of –153°C (–243°F) at the landing site, while VIRTIS, an instrument on the primary spacecraft Rosetta, has measured -70°C (-94°F) at present. These temperatures will rise as perihelion is reached on August 13, 2015, at a distance of 1.2432 A.U. (24% further from the Sun than Earth). At present – January 23rd – 67P is 2.486 A.U. from the Sun (2 1/2 times farther from the Sun than Earth). While not a close approach to the Sun for a comet, the Solar radiation intensity will increase by 4 times between the present (January 2014) and perihelion in August.

Hubble capture a sequence of images of the comet 73P/Schwassman-Wachmann 3. The comet fragmented and like 73P, Rosetta's 67P will likely breakup some day in two majore fragments with debris spreading out as in these images. The Solar wind pressure as well as any explosive force from the breakup causes the comet fragments to slowly disperse but altogether remain effectively in the same orbit. (Image Credit: NASA/Hubble)
Hubble captured a sequence of images of the comet 73P/Schwassman-Wachmann 3. The comet fragmented, and like 73P, Rosetta’s 67P will likely break some day into two major fragments with debris spreading out as in these images. The Solar wind pressure, as well as any explosive force from the break up, will cause the comet fragments to slowly disperse but effectively remain in the same orbit. (Image Credit: NASA/Hubble)

Stresses due to temperature changes from diurnal variations, the changing Sun angle during perihelion approach, from loss of material, and finally from changes in the tidal forces on a daily basis (12.4043 hours) may lead to changes in the fissure causing it to possibly widen or increase in length. Rosetta will continue escorting the comet and delivering images of the whole surface that will give Rosetta scientists the observations and measurements to determine 67P/Churyumov–Gerasimenko’s condition now and its fate in the longer term.

The fissure is not a very recent event. Universe Today's Bob King published an earlier image in his blog in September and added a question to illustrate. Whether the crack has widen since this time is not certain. (Image Credit: ESA, Illustration, Bob King)
The fissure is not a very recent event. Universe Today’s Bob King published an earlier image in his blog in September and added a question to illustrate. Whether the crack has widened since that time is not certain. (Image Credit: ESA, Illustration, Bob King)

Stay tuned for a forthcoming article from UT’s writer Bob King about numerous Rosetta mission scientific findings published this week in the journal Science.

Reference:

The morphological diversity of comet 67P/Churyumov-Gerasimenko

On the nucleus structure and activity of comet 67P/Churyumov-Gerasimenko

Look Out Below! Rosetta Will Give Its Comet A Close Buzz In February

A mosaic of images of Comet 67P/Churyumov–Gerasimenko taken from the Rosetta spacecraft Dec. 14. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Remember how breathless we felt when the Philae lander actually made it to the surface of its target comet a few weeks ago? Sure, the maneuvers didn’t go as planned, but the images the spacecraft obtained in its brief spurts of activity on the surface are still being shared and discussed eagerly by scientists (amid a controversial image release policy, to be sure.)

Well, the truck delivery for Philae — the Rosetta spacecraft, still doing maneuvers above — is going to do something special in February. The machine is going to scoot down real close to the comet, just before heating from the Sun could make it dangerous to do so due to gas and dust emissions.

The plan is to bring Rosetta to an astounding four miles (six kilometers) above Comet 67P/Churyumov–Gerasimenko, so close that the images sent back to Earth will have a resolution of just a few inches per pixel. Scientists hope to learn more about how reflective the comet is and also to better understand how gas is emitted as 67P draws close to the Sun.

A mosaic of images of Comet 67P/Churyumov–Gerasimenko taken from the Rosetta spacecraft Dec. 14. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
A mosaic of images of Comet 67P/Churyumov–Gerasimenko taken from the Rosetta spacecraft Dec. 14. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

“As the comet becomes more and more active, it will not be possible to get so close to the comet. So this opportunity is very unique,” stated Matt Taylor, the Rosetta project scientist from the European Space Research and Technology Center, in a NASA press release.

Rosetta’s closest view of the comet previous to this was a six-mile (10 kilometer) mapping orbit that it did for a short time before moving to release the Philae lander. After that, its orbit was expected to range between 20 km and 50 km (12.4 miles and 18.6 miles) through the end of this month.

Philae, meanwhile, made it down to the surface and did manage to send pictures back during its approximately 60 hours of activity, before shutting down due to a lack of sunlight hitting its solar panels. Philae is now wedged in a shady spot on the comet, but it’s possible more sunlight could fall in that area when the comet nears its closest approach to the Sun in 2015, between the orbits of Earth and Mars.

A handful of pictures from Philae were released or re-released publicly last week through ESA and NASA, with far more being shown at the American Geophysical Union annual meeting (see video above, and this link that requires free registration).

The European Space Agency is saying that about 20% of the mission’s science is expected to flow from Philae (at most), and 80% from Rosetta. Early results from both spacecraft present some intriguing properties about the comet. Based on the ratio of isotopes (types) of hydrogen on the comet, it’s more likely that it was asteroids that delivered water to Earth. Also, Philae was unable to dig very far into the surface, implying that underneath the dust must be something like a thick layer of ice.

A recent Rosetta blog post on the European Space Agency says that the team expects to take a break for the holidays from posting — unless, of course, they manage to track down the Philae lander in pictures. The location of the spacecraft is still unknown, but it’s believed that Rosetta’s high-resolution camera may be able to catch the lander or its glint — coupled with clues Philae’s experiments gave to its location.

Rosetta’s Instruments Direct Scientists to Look Elsewhere for the Source of Earth’s Water

Illustration of a rocky planet being bombarded by comets. (Image credit: NASA/JPL-Caltech)
Illustration of a rocky planet being bombarded by comets. (Image credit: NASA/JPL-Caltech)

Where did all of our water come from? What might seem like a simple question has challenged and intrigued planetary scientists for decades. So results just released by Rosetta mission scientists have been much anticipated and the observations of the Rosetta spacecraft instruments are telling us to look elsewhere. The water of comet 67P/Churyumov-Gerasimenko does not resemble Earth’s water.

Because the Earth was extremely hot early in its formation, scientists believe that Earth’s original water should have boiled away like that from a boiling kettle. Prevailing theories have considered two sources for a later delivery of water to the surface of the Earth once conditions had cooled. One is comets and the other is asteroids. Surely some water arrived from both sources, but the question has been which one is the predominant source.

There are two areas of our Solar System in which comets formed about 4.6 billion years ago. One is the Oort cloud far beyond Pluto. Everything points to Comet 67P’s origins being the other birthplace of comets – the Kuiper Belt in the region of Neptune and Pluto. The Rosetta results are ruling out Kuiper Belt comets as a source of Earth’s water. Previous observations of Oort cloud comets, such as Hyakutake and Hale-Bopp, have shown that they also do not have Earth-like water. So planetary scientists must reconsider their models with weight being given to the other possible source – asteroids.

The question of the source of Earth’s water has been tackled by Earth-based instruments and several probes which rendezvous with comets. In 1986, the first flyby of a comet – Comet 1P/Halley, an Oort cloud comet – revealed that its water was not like the water on Earth. How the water from these comets –Halley’s and now 67P – differs from Earth’s is in the ratio of the two types of hydrogen atoms that make up the water molecule.

Illustration of the Rosetta spacecraft showing the location of the ROSINA mass spectrometer instrument, DFMS. The difference between a Deuterium and Hydrogen atom are also illustrated. A water molecule with Deuterium is known as heavy water due to the additional mass of D vs. H (an extra neutron). (Credit: ESA/Rosetta)
Illustration of the Rosetta spacecraft showing the location of the ROSINA mass spectrometer instrument, DFMS. The difference between a Deuterium and Hydrogen atom is also illustrated. A water molecule with Deuterium is known as heavy water due to the additional mass of Dueterium vs. Hydrogen (i.e., an extra neutron). (Credit: ESA/Rosetta)

Measurements by spectrometers revealed how much Deuterium  – a heavier form of the Hydrogen atom – existed in relation to the most common type of Hydrogen in these comets. This ratio, designated as D/H, is about 1 in 6000 in Earth’s ocean water. For the vast majority of comets, remote or in-situ measurements have found a ratio that is higher which does not support the assertion that comets delivered water to the early Earth surface, at least not much of it.

Most recently, Hershel space telescope observations of comet Hartley 2 (103P/Hartley) caused a stir in the debate of the source of Earth’s water. The spectral measurements of the comet’s light revealed a D/H ratio just like Earth’s water. But now the Hershel observation has become more of an exception because of Rosetta’s latest measurements.

A plot displaying the Deuterium/Hydrogen (D/H) ratio of Solar System objects. Only asteroids have a D/H ratio that matches the Earths and comets with the exception of two so far measured have higher ratios. Objects are grouped by color. Planets & moons (blue), chrondritic meteorites from the asteroid belt (grey), Oort cloud comets(purple), Jupiter family comets(pink). Diamond markers = In Situ measurements, Circles = remote astronomical measurements(Credit: Altwegg et al. 2014)
A plot displaying the Deuterium/Hydrogen (D/H) ratio of Solar System objects. Asteroids have a D/H ratio that matches that of the Earth, while comets – except for two measured to date – have higher ratios. Objects are grouped by color: planets & moons (blue), chrondritic meteorites from the asteroid belt (grey), Oort cloud comets (purple), and Jupiter family comets (pink). Diamond markers = In Situ measurements; circles = remote astronomical measurements. (Credit: Altwegg, et al. 2014)

The new measurements of 67P were made by the ROSINA Double Focusing Mass Spectrometer (DFMS) on board Rosetta. Unlike remote observations using light which are less accurate, Rosetta was able to accurately measure the quantities of Deuterium and common Hydrogen surrounding the comet. Scientists could then simply determine a ratio. The results are reported in the paper “67P/Churyumov-Gerasimenko, a Jupiter Family Comet with a high D/H ratio” by K. Altwegg, et al., published in the 10 December 2014 issue of Science.

New Rosetta mission findings do not exclude comets as a source of water in and on the Earth's crust but does indicate comets were a minor contribution. A four-image mosaic comprises images taken by Rosetta’s navigation camera on 7 December from a distance of 19.7 km from the centre of Comet 67P/Churyumov-Gerasimenko. (Credit: ESA/Rosetta/Navcam Imager)
New Rosetta mission findings do not exclude comets as a source of water in and on the Earth’s crust but does indicate comets were a minor contribution. A four-image mosaic comprises images taken by Rosetta’s navigation camera on 7 December from a distance of 19.7 km from the centre of Comet 67P/Churyumov-Gerasimenko. (Credit: ESA/Rosetta/Navcam Imager)

The ROSINA instrument observations determined a ratio of 5.3 ± 0.7 × 10-4, which is approximately 3 times the ratio of D/H for Earth’s water. These results do not exclude comets as a source of terrestrial water but they do redirect scientists to consider asteroids as the predominant source. While asteroids have much lower water content compared with comets, asteroids, and their smaller versions, meteoroids, are more numerous than comets. Every meteor/falling star that we see burning up in our atmosphere delivers a myriad of compounds, including water, to Earth. Early on, the onslaught of meteoroids and asteroids impacting Earth was far greater. Consequently, the small quantities of water added delivered by each could add up to what now lies in the oceans, lakes, streams, and even our bodies.

References:

D/H Ratio of Water on Earth Measured with DFMS

67P/Churyumov-Gerasimenko, a Jupiter family comet with a high D/H ratio

Rosetta fuels the debate on the Origin of Earth’s Water

The Provenances of Asteroids, and Their Contributions to the Volatile Inventories of the Terrestrial Planets

Recent Universe Today related article:

What Percent of Earth is Water?

Philae Lander Early Science Results: Ice, Organic Molecules and Half a Foot of Dust

Philae's MUPUS probe took temperature measurements and hammered into the surface at the landing site to discover the lander alighted on some very hard ice. Credit: ESA

An uncontrolled, chaotic landing.  Stuck in the shadow of a cliff without energy-giving sunlight.  Philae and team persevered.  With just 60 hours of battery power, the lander drilled, hammered and gathered science data on the surface of comet 67P/Churyumov-Gerasimenko before going into hibernation. Here’s what we know. 

Despite appearances, the comet’s hard as ice. The team responsible for the MUPUS (Multi-Purpose Sensors for Surface and Sub-Surface Science) instrument hammered a probe as hard as they could into 67P’s skin but only dug in a few millimeters:

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
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. At the final landing site, it’s believed that Times are CST. Philae’s 3.3 feet (1-m) across. Credit: ESA

“Although the power of the hammer was gradually increased, we were not able to go deep into the surface,” said Tilman Spohn from the DLR Institute of Planetary Research, who leads the research team. “If we compare the data with laboratory measurements, we think that the probe encountered a hard surface with strength comparable to that of solid ice,” he added. This shouldn’t be surprising, since ice is the main constituent of comets, but much of 67P/C-G appears blanketed in dust, leading some to believe the surface was softer and fluffier than what Philae found.

This finding was confirmed by the SESAME experiment (Surface Electrical, Seismic and Acoustic Monitoring Experiment) where the strength of the dust-covered ice directly under the lander was “surprisingly high” according to Klaus Seidensticker from the DLR Institute. Two other SESAME instruments measured low vaporization activity and a great deal of water ice under the lander.

As far as taking the comet’s temperature, the MUPUS thermal mapper worked during the descent and on all three touchdowns. At the final site, MUPUS recorded a temperature of –243°F (–153°C) near the floor of the lander’s balcony before the instrument was deployed. The sensors cooled by a further 10°C over a period of about a half hour:

The location of Philae's first touchdown on the surface of Comet 67P/C-G. Although covered in dust in many areas, Philae found strong evidence for firm ice beneath. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
The location of Philae’s first touchdown on the surface of Comet 67P/C-G. Although covered in dust in many areas, Philae found strong evidence for firm ice beneath the comet’s surface. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

“We think this is either due to radiative transfer of heat to the cold nearby wall seen in the CIVA images or because the probe had been pushed into a cold dust pile,” says Jörg Knollenberg, instrument scientist for MUPUS at DLR. After looking at both the temperature and hammer probe data, the Philae team’s preliminary take is that the upper layers of the comet’s surface are covered in dust 4-8 inches (10-20 cm), overlaying firm ice or ice and dust mixtures.

The ROLIS camera (ROsetta Lander Imaging System) took detailed photos during the first descent to the Agilkia landing site. Later, when Philae made its final touchdown, ROLIS snapped images of the surface at close range. These photos, which have yet to be published, were taken from a different point of view than the set of panorama photos already received from the CIVA camera system.

During Philae’s active time, Rosetta used the CONSERT (COmet Nucleus Sounding Experiment by Radio wave Transmission) instrument to beam a radio signal to the lander while they were on opposite sides of the comet’s nucleus. Philae then transmitted a second signal through the comet back to Rosetta. This was to be repeated 7,500 times for each orbit of Rosetta to build up a 3D image of 67P/C-G’s interior, an otherworldly “CAT scan” as it were.  These measurements were being made even as Philae lapsed into hibernation. Deeper down the ice becomes more porous as revealed by measurements made by the orbiter.

Rosetta’s Philae lander includes a carefully selected set of instruments and is being prepared for a November 11th dispatch to analyze a comet’s surface. Credit: ESA, Composite – T.Reyes
Rosetta’s Philae lander includes a carefully selected set of instruments to analyze a comet’s surface. Credit: ESA, Composite – T.Reyes

The last of the 10 instruments on board the Philae lander to be activated was the SD2 (Sampling, Drilling and Distribution subsystem), designed to provide soil samples for the COSAC and PTOLEMY instruments. Scientists are certain the drill was activated and that all the steps to move a sample to the appropriate oven for baking were performed, but the data right now show no actual delivery according to a tweet this morning from Eric Hand, reporter at Science Magazine. COSAC worked as planned however and was able to “sniff” the comet’s rarified atmosphere to detect the first organic molecules. Research is underway to determine if the compounds are simple ones like methanol and ammonia or more complex ones like the amino acids.

Stephan Ulamec, Philae Lander manager, is confident that we’ll resume contact with Philae next spring when the Sun’s angle in the comet’s sky will have shifted to better illuminate the lander’s solar panels. The team managed to rotate the lander during the night of November 14-15, so that the largest solar panel is now aligned towards the Sun. One advantage of the shady site is that Philae isn’t as likely to overheat as 67P approaches the Sun en route to perihelion next year. Still, temperatures on the surface have to warm up before the battery can be recharged, and that won’t happen until next summer.

Let’s hang in there. This phoenix may rise from the cold dust again.

Sources: 1, 2

Alone and Confused, Philae Breaks our Hearts

The Philae that could! The lander photographed during its descent by Rosetta. Credit: ESA/Rosetta/MPS for Rosetta Team/

I was twelve years old when Columbia disintegrated. Space exploration was not even a particular interest of mine at the time, but I remember exactly where I was when the news came.  My dad and I were sitting in the living room of my childhood home, listening to NPR. I don’t really recall how I felt when they broke into our program with the news, but I remember well the two emotions that seemed to permeate the coverage that soon become constant: confusion and sadness. As I watched the almost surreal saga of ESA’s Philae this week, I found my mind wandering back to that day eleven years ago. That confusion rang out was hardly surprising; after all, things weren’t going right and we didn’t know why. But it was the sadness, I think, that drew my mind into the past. Many of the countless people watching Philae’s distress unfold before us weren’t merely disappointed that a decades-in-the-making experiment wasn’t going as planned. The word heartbroken kept springing to mind.

Let me be unequivocal: the loss of a machine, no matter how valuable or beloved, pales in comparison to the forfeit of human life. The astronauts lost on Columbia, like those snatched from us before and since, left behind families, friends, and a grateful world. But, why, then, did it seem to feel so similar to so many people?

 “This is legitimately upsetting” a friend and colleague texted me on Friday as it became clear that the tiny lander’s batteries were beginning to run dry. She was far from alone in her sentiment. Across Twitter, people from around the world seemed to be lashing out against the helplessness of the situation.

https://twitter.com/asamsaktha/status/533700062673928193

And, in conversations I had with other scientists at the 46th annual Division for Planetary Sciences meeting in Tucson, AZ this week, people seemed almost mournful at the prospect of the lander’s loss. These same researchers had laughed and cheered just days earlier when shown the crater made by NASA’s LADEE spacecraft upon its crash into the lunar surface.

 The questions in my mind are numerous. What’s the cause of this inequity? Why do we seem to latch onto certain spacecraft and blithely ignore others? What is it that makes us become emotionally attached to machines in the first place? 

In part, I think, our attachment comes from the unprecedented view offered to us by social media. In 1990, an event not so dissimilar from this one beset NASA’s Galileo spacecraft. Flying by the Earth on its way to Jupiter, Galileo had just attempted to unfurl its main antenna, a maneuver critical to the mission’s success.  In mission control, they received the bad news: the antenna was stuck. But, the world did not break down in despair. In the days to come, stories would appear in newspapers and on the nightly news, but a world where even email was in its infancy lacked a means for the average citizen to follow along with every detail. 

Nineteen years later, this would not be the case. As soon as it became clear to those in ESA headquarters that something had gone very wrong during Philae’s descent, we all knew. And, as data began to trickle in about one bounce off the surface and then another, we all cringed. When the last power drained from the lander’s batteries, we followed along, one volt after another. Philae may have been the pride of the ESA scientists and engineers who designed it, but it felt like it was ours. 

But, it didn’t feel like ours in the way that a car or a plane or even a space station does. It felt like our friend. No doubt, this can be directly linked to the first person point of view employed for its Twitter account. Instead of the @Phillae2014 account reporting “the Ptolemy instrument has made a measurement,” we get “I just completed a @Philae_Ptolemy measurement!!” It seems like a small change, but it opens up a whole new world of connection with this distant traveler. At no time was this clearer than when things started to go wrong.

 How poignant is that? Two travelers talking to one another from across the solar system. But, as Philae’s time began to wind down, the messages tugged even more urgently on our heartstrings.

And, it all pales in comparison to the way China’s Yutu rover signed off when it looked like a malfunction might cause it to freeze to death on the Moon (original Chinese, CNN translation):

… my masters discovered something abnormal with my mechanical control system. …I’m aware that I might not survive this lunar night…

The sun has fallen, and the temperature is dropping so quickly… to tell you all a secret, I don’t feel that sad. I was just in my own adventure story – and like every hero, I encountered a small problem.

Goodnight, Earth. Goodnight, humanity.

Talk about heartbreaking.

This personal point of view combines particularly effectively with landers and rovers. These craft seem more human than ships like Cassini or Galileo, with their silent glide through deep space. When something goes wrong with a surface explorer, as it did with Philae or Yutu, it plays on our deepest fears. Every time we’re lost, the little voice of panic begins to creep into our thoughts: “what if this is the time that I can’t get back?” Reading the “thoughts” of a tiny spacecraft, lost and alone and confused, puts us right there ourselves. As mission controllers edged towards desperation in their attempts to save the stricken explorer, we knew how that delirious urgency felt. Our attachment becomes almost unavoidable. 

So, what does this all mean? I think it’s a clear signal that people are engaged by the exploration of space. When it comes to us in the right way, on our terms, it’s a big hit. By anthropomorphizing these robots, we humanize the science that they do. Suddenly a machine more than 500 million kilometers away becomes more relatable than the scientists next door who control it. Perhaps ESA, NASA, and other space agencies can extend this relationship even further. Rather than springing to “life” upon liftoff, spacecraft can share with us their view of the entire process, starting not from space, but from the first drawings on an engineer’s blackboard.

One thing’s for sure, though. A relationship like that won’t make times like these any easier to handle.

Music to Celebrate the Rosetta Mission

We report on the Rosetta mission to share the news and follow the progress of the precarious-perched Philae. But sometimes it takes another form of communication to dig down deep and release the wonder we all feel inside at the amazing images that daily light up our monitors. Music. Inspired by the Rosetta mission and in celebration of it, Vangelis composed three pieces of music set to slide shows featuring beautiful imagery of comet 67P/C-G and Philae.  Continue reading “Music to Celebrate the Rosetta Mission”

New Images from Philae Reveal Comet’s Ancient Surface

First panorama sent by Philae from the surface of the comet. At upper right we see the reflection of the Sun and the top of the CONSERT instrument antenna. Credit: ESA

We may not know exactly where Philae is, but it’s doing a bang-up job sending its first photos from comet 67P/Churyumov-Gerasimenko. After bouncing three times on the surface, the lander is tilted vertically with one foot in open space in a “handstand” position.  When viewing the photographs, it’s good to keep that in mind. 

Philae landed nearly vertically on its side with one leg up in outer space. Here we see it in relation to the panoramic photos taken with the CIVA cameras. Credit: ESA
Philae landed nearly vertically on its side with one leg up in outer space. Here we see it in relation to the panoramic photos taken with the CIVA cameras. Credit: ESA

Although it’s difficult to say how far away the features are in the image. In an update today at a press briefing, Jean Pierre Biebring, principal investigator of CIVA/ROLIS (lander cameras), said that the features shown in the frame at lower left are about 1-meter or 3 feet away. Philae settled into its final landing spot after a harrowing first bounce that sent it flying as high as a kilometer above the comet’s surface.

After hovering for two hours, it landed a second time only to bounce back up again a short distance – this time 3 cm or about 1.5 inches. Seven minutes later it made its third and final landing. Incredibly, the little craft still functions after trampolining for hours!

Stephan Ulamec, Philae Lander manager, describes how Philae first landed less than 100 meters from the planned Agilkia site (red square). Without functioning harpoons and thrusters to fix it to the ground there, it rebounded and shot a kilometer above the comet. Right now, it's somewhere in the blue diamond. Credit: ESA
Stephan Ulamec, Philae Lander manager, describes how Philae first landed less than 100 meters from the planned Agilkia site (red square). Without functioning harpoons and thrusters to fix it to the ground there, it rebounded and shot a kilometer above the comet. Right now, it’s somewhere in the blue diamond. Credit: ESA

Despite its awkward stance, Philae continues to do a surprising amount of good science. Scientists are still hoping to come up with a solution to better orientate the lander. Their time is probably limited. The craft landed in the shadow of a cliff, blocking sunlight to the solar panels used to charge its  battery. Philae receives only 1.5 hours instead of the planned 6-7 hours of sunlight each day. That makes tomorrow a critical day.  Our own Tim Reyes of Universe Today had this to say about Philae’s power requirements:

Rosetta’s lander Philae is safely on the surface of Comet 67P/Churyumov-Gerasimenko, as these first two CIVA images confirm. One of the lander’s three feet can be seen in the foreground. The image is a two-image mosaic. Credit: ESA/Rosetta/Philae/CIVA
One of the lander’s three feet can be seen in the foreground in this high-resolution two-image mosaic. Credit: ESA/Rosetta/Philae/CIVA

“Philae must function on a small amount of stored energy upon arrival: 1000 watt-hours (equivalent of a 100 watt bulb running for 10 hours). Once that power is drained, it will produce a maximum of 8 watts of electricity from solar panels to be stored in a 130 watt-hour battery.” You can read more about Philae’s functions in Tim’s recent article.

Ever inventive, the lander team is going to try and nudge Philae into the sunlight by operating the moving instrument called MUPUS tonight. The operation is a delicate one, since too much movement could send the probe flying off the surface once again.

Here are additional photos from the press conference showing individual segments of the panorama and other aspects of Philae’s next-to-impossible landing. As you study the crags and boulders, consider how ancient this landscape is. 67P originated in the Kuiper Belt, a large reservoir of small icy bodies located just beyond Neptune, more than 4.5 billion years ago. Either through a collision with another comet or asteroid, or through gravitational interaction with other planets, it was ejected from the Belt and fell inward toward the Sun.

Astronomers have analyzed its orbit and discovered that up until 1840, the future comet 67P never came closer than 4 times Earth’s distance from the Sun, ensuring that its ices remained as pristine as the day they formed. After that date, the comet passed near Jupiter and its orbit changed to bring it within the inner Solar System. We’re seeing a relic, a piece of dirty ice rich with history. Even a Rosetta stone of its own we can use to interpret the molecular script revealing the origin and evolution of comets.

Philae falls to the craggy comet photographed by the Rosetta mothership. Credit: ESA
Philae falls to the craggy comet photographed by the Rosetta mothership. Credit: ESA
An image of Comet 67P/Churyumov–Gerasimenko at less than 10 km from its surface. This selection of previously unpublished ‘beauty shots’, taken by Rosetta’s navigation camera, presents the varied and dramatic terrain of this mysterious world from this close orbit phase of the mission. Credit: ESA.
An image of Comet 67P/Churyumov–Gerasimenko at less than 10 km from its surface. This selection of previously unpublished ‘beauty shots’, taken by Rosetta’s navigation camera, presents the varied and dramatic terrain of this mysterious world from this close orbit phase of the mission. Credit: ESA.
Frame from panoramic image. Credit: ESA
Frame from panoramic image. This has been heavily toned to reveal details in the shadow of the cliff. Credit: ESA
Frame from panoramic image. Credit: ESA
Frame from panoramic image. Credit: ESA
Frame from panoramic image. Credit: ESA
Frame from panoramic image. Credit: ESA
Frame from panoramic image. Credit: ESA
Frame from panoramic image. Credit: ESA
Frame from panoramic image. Credit: ESA
Frame from panoramic image. Credit: ESA
Image from the Philae lander as it approached the surface. The dust-covered boulder at upper right is about 5 meters (16.4 feet) across. The dust might have originated through vaporization of ice on the boulder itself or deposited there by dust settling from jets elsewhere.  Credit: ESA
Image from the Philae lander as it approached the surface. The dust-covered boulder at upper right is about 5 meters (16.4 feet) across. The dust might have originated through vaporization of ice in the boulder itself or settled there from active jets elsewhere on the comet. Credit: ESA

 

We Land on a Comet Today! Updates on Philae’s Progress

Just released "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. Credit: ESA/Rosetta/Philae/CIVA

Anticipation is intense as the Philae lander free-falls to the surface of Comet Churyumov-Gerasimenko this morning. The final “Go” for separation from the Rosetta spacecraft was given around 2:30 a.m.; Philae’s now well on its way to Agilkia, the target landing site atop the 67P/C-G’s largerEverything is running smoothly except for one potential problem. During checks on the lander’s health, it was discovered that the active descent system, which provides a thrust to avoid rebound at the moment of touchdown, can’t be activated.

Artist impression of Philae separating from Rosetta earlier this morning. The lander is now free-falling to the comet under the influence of its gravity. Credit: ESA
Artist impression of Philae separating from Rosetta earlier this morning. The lander is now free-falling to the comet under the influence of its gravity. Credit: ESA

At touchdown, as Philae anchors itself to the comet with harpoons and ice screws on each of its legs, the thruster on top of the lander is supposed to push it down to counteract the force of the harpoon firing in the opposite direction.

Klim Churyumov (left) Svetlana Gerasimenko are both at ESA today during the historic landing on the comet they discovered on September 20, 1969. Credit: ESA TV
Klim Churyumov (left) Svetlana Gerasimenko are both at ESA today during the historic landing on the comet they discovered on September 20, 1969. Credit: ESA TV

“The cold gas thruster on top of the lander does not appear to be working so we will have to rely fully on the harpoons at touchdown,”says Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center.

The Philae that could! The lander photographed during its descent by Rosetta. Credit: ESA/Rosetta/MPS for Rosetta Team/
The Philae that could! The lander photographed during its descent by Rosetta. Credit: ESA/Rosetta/MPS for Rosetta Team/

Philae is on target to land on the comet around 9:37 a.m. CST (15:37 UT). Confirmation of touchdown will take about 28 minutes as the signal, traveling at the speed of light, works its way back on Earth. As Philae floats down to the comet it not only has to deal with the 67P/C-G’s gravity but also the cloud of dust and ice grains escaping from the surface. Check back for regular updates and photos!

Tense control room during the  Philae landing confirmation. Credit: ESA
Tense control room during the Philae landing confirmation Time: 9:48 a.m. CST. Credit: ESA