This was the Snowstorm Rosetta Saw When it Got 79 km Away From Comet 67P

In August of 2014, the ESA’s Rosetta mission made history when it rendezvoused with the Comet 67P/Churyumov–Gerasimenko. For the next two years, the probe flew alongside the comet and conducted detailed studies of it. And in November of 2014, Rosetta deployed its Philae probe onto the comet, which was the first time in history that a lander was deployed to the surface of a comet.

During the course of its mission, Rosetta revealed some truly remarkable things about this comet, including data on its composition, its gaseous halo, and how it interacts with solar wind. In addition, the probe also got a good look at the endless stream of dust grains that were poured from the comet’s surface ice as it approached the Sun. From the images Rosetta captured, which the ESA just released, it looked a lot like driving through a snowstorm!

The image below was taken two years ago (on January 21st, 2016), when Rosetta was at a distance of 79 km from the comet. At the time, Rosetta was moving closer following the comet reaching perihelion, which took place during the previous August. When the comet was at perihelion, it was closer to the Sun and at its most active, which necessitated that Rosetta move farther away for its own protection.

Image of the dust and particles the Rosetta mission was exposed to as it flew alongside Comet 67P/Churyumov–Gerasimenko. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

As you can see from the image, the environment around the comet was extremely chaotic, even though it was five months after the comet was at perihelion. The white streaks reveal the dust grains as they flew in front of Rosetta’s camera over the course of a 146 second exposure. For the science team directing Rosetta, flying the spacecraft through these dust storms was like trying to drive a car through a blizzard.

Those who have tried know just how dangerous this can be! On the one hand, visibility is terrible thanks to all the flurries. On the other, the only way to stay oriented is to keep your eyes pealed for any landmarks or signs. And all the while, there is the danger of losing control and colliding with something. In much the same way, passing through the comet’s dust storms was a serious danger to the spacecraft.

In addition to the danger of collisions, flying through these clouds was also hazardous for the spacecraft’s navigation system. Like many robotic spacecraft, Rosetta relies on star trackers to orient itself – where it recognizes patterns in the field of stars to orient itself with respect to the Sun and Earth. When flying closer to the comet, Rosetta’s star trackers would occasionally become confused by dust grains, causing the craft to temporarily enter safe mode.

Artist’s impression of the Rosetta probe signalling Earth. Credits: ESA-C.Carreau

This occurred on March 28th, 2015 and again on May 30th, 2016, when Rosetta was conducting flybys that brought it to a distance of 14 and 5 km from the comet’s surface, respectively. On both occasions, Rosetta’s navigation system suffered from pointing errors when it began tracking bright dust grains instead of stars. As a result, on these occasions, the mission team lost contact with the probe for 24 hours.

As Patrick Martin, the ESA’s Rosetta mission manager, said during the second event:

“We lost contact with the spacecraft on Saturday evening for nearly 24 hours. Preliminary analysis by our flight dynamics team suggests that the star trackers locked on to a false star – that is, they were confused by comet dust close to the comet, as has been experienced before in the mission.”

Despite posing a danger to Rosetta’s solar arrays and its navigation system, this dust is also of high scientific interest. During the spacecraft’s flybys, three of its instruments studied tens of thousands of grains, analyzing their composition, mass, momentum and velocity, and also creating 3D profiles of their structure. By studying these tiny grains, scientists were also able to learn more about the bulk composition of comets.

Another snapshot of Comet 67P/Churyumov–Gerasimenko’s dusty emissions, taken on Jan. 21st, 2016. Credit: ESA

Before it reached its grand finale and crashed into the comet’s surface on September 30th, 2016, Rosetta made some unique scientific finds about the comet. These included mapping the comet’s surface features, discerning its overall shape, analyzing the chemical composition of its nucleus and coma, and measuring the ratio of water to heavy water on its surface.

All of these findings helped scientists to learn more about how our Solar System formed and evolved, and shed some light on how water was distributed throughout our Solar System early in its history. For instance, by determining that the ratio of water to heavy water on the comet was much different than that of Earth’s, scientists learned that Earth’s water was not likely to have come from comets like Comet 67P/Churyumov–Gerasimenko.

On top of that, the spacecraft took more than a hundred thousand image of the comet with its high-resolution OSIRIS camera (including the ones shown here) and its navigation camera. These images can be perused by going to the ESA’s image browser archive. I’m sure you’ll agree, they are all as beautiful as they are scientifically relevant!

Further Reading: ESA

Rosetta Team Finds New, Final Image Hiding in the Data

ESA scientists have found one additional image from the Rosetta spacecraft hiding in the telemetry. This new image was found in the last bits of data sent by Rosetta immediately before it shut down on the surface of Comet 67P/Churyumov–Gerasimenko last year.

The new image shows a close-up shot of the rocky, pebbly surface of the comet, and looks somewhat reminiscent of the views the Huygens lander took of the surface of Saturn’s moon Titan.

A final image from Rosetta, shortly before it made a controlled impact onto Comet 67P/Churyumov–Gerasimenko on 30 September 2016. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

Planetary astronomer Andy Rivkin noted on Twitter that for size context, he estimates the block just right of center looks to be about the size of a hat. That’s a fun comparison to have (not to mention thinking about hats on Comet 67P!)

The picture has a scale of 2 mm/pixel and measures about 1 m across. It’s a really ‘close’ close-up of Comet 67P.

“The last complete image transmitted from Rosetta was the final one that we saw arriving back on Earth in one piece moments before the touchdown at Sais,” said Holger Sierks, principal investigator for the OSIRIS camera at the Max Planck Institute for Solar System Research in Göttingen, Germany. “Later, we found a few telemetry packets on our server and thought, wow, that could be another image.”

The team explains that the image data were put into telemetry ‘packets’ aboard Rosetta before they were transmitted to Earth, and the final images were split into six packets. However, for the very last image, the transmission was interrupted after only three full packets. The incomplete data was not recognized as an image by the automatic processing software, but later, the engineers in Göttingen could make sense of these data fragments to reconstruct the image.

You’ll notice it is rather blurry. The OSIRIS camera team says this image only has about 53% of the full data and “therefore represents an image with an effective compression ratio of 1:38 compared to the anticipated compression ratio of 1:20, meaning some of the finer detail was lost.”

That is, it gets a lot blurrier as you zoom in compared with a full-quality image. They compared it to compressing an image to send via email, versus an uncompressed version that you would print out and hang on your wall.

Rosetta’s final resting spot is in a region of active pits in the Ma’at region on the two-lobed, duck-shaped comet.

A montage of the last few images from Rosetta, including the new image, with context of where the features on the last images are located. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Launched in 2004, Rosetta traveled nearly 8 billion kilometers and its journey included three Earth flybys and one at Mars, and two asteroid encounters. It arrived at the comet in August 2014 after being in hibernation for 31 months.

After becoming the first spacecraft to orbit a comet, it deployed the Philae lander in November 2014. Philae sent back data for a few days before succumbing to a power loss after it unfortunately landed in a crevice and its solar panels couldn’t receive sunlight.

But Rosetta showed us unprecedented views of Comet 67P and monitored the comet’s evolution as it made its closest approach and then moved away from the Sun. However, Rosetta and the comet moved too far away from the Sun for the spacecraft to receive enough power to continue operations, so the mission plan was to set the spacecraft down on the comet’s surface.

And scientists have continued to sift through the data, and this new image was found. Who knows what else they’ll find, hiding the data?

Read more details about this image at ESA’s website.

Read our article about Rosetta’s mission end here.

Rosetta Images Show Comet’s Changing Surface Close Up

The Rosetta spacecraft learned a great deal during the two years that it spent monitoring Comet 67P/Churyumov-Gerasimenko – from August 6th, 2014 to September 30th, 2016. As the first spacecraft to orbit the nucleus of a comet, Rosetta was the first space probe to directly image the surface of a comet, and observed some fascinating things in the process.

For instance, the probe was able to document some remarkable changes that took place during the mission with its OSIRIS camera. According to a study published today (March. 21st) in Science, these included growing fractures, collapsing cliffs, rolling boulders and moving material on the comet’s surface that buried some features and exhumed others.

These changes were noticed by comparing images from before and after the comet reached perihelion on August 13th, 2015 – the closets point in its orbit around the Sun. Like all comets, it is during this point in 67P/Churyumov-Gerasimenko’s orbit that the surface experiences its highest levels of activity, since perihelion results in greater levels of surface heating, as well as increased tidal stresses.

Images taken by Rosetta’s OSIRIS camera show changes in the surface between 2015 and 2016. Credit: ESA/Rosetta/NAVCAM (top center images); ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA (all others)

Basically, as comets gets closer to the Sun, they experience a combination of in-situ weathering and erosion, sublimation of water-ice, and mechanical stresses arising from an increased spin rate. These processes can be either unique and transient, or they can place over longer periods of time.

As Ramy El-Maarry, a scientist from the Max-Planck Institute for Solar System Research and the lead author of the study, said in an ESA press statement:

“Monitoring the comet continuously as it traversed the inner Solar System gave us an unprecedented insight not only into how comets change when they travel close to the Sun, but also how fast these changes take place.”

For instance, in-situ weathering occurs all over the comet and is the result of heating and cooling cycles that happen on both a daily and a seasonal basis. In the case of 67P/Churyumov-Gerasimenko’s (6.44 Earth years), temperatures range from 180 K (-93 °C; -135 °F) to 230 K (-43 °C; -45 °F) during the course of its orbit. When the comet’s volatile ices warm, they cause consolidated material to weaken, which can cause fragmentation.

Combined with the heating of subsurface ices – which leads to outgassing – this process can result in the sudden collapse of cliff walls. As other photographic evidence that was recently released by the Rosetta science team can attest, this sort of process appears to have taken place in several locations across the comet’s surface.

Images showing a new fracture and boulder movement in Anuket. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/ID

Similarly, comets experience increased stress because their spin rates speed up as they gets closer to the Sun. This is believed to be what caused the 500 meter-long (1640 ft) fracture that has been observed in the Anuket region. Originally discovered in August of 2014, this fracture appeared to have grown by 30 meters (~100 ft) when it was observed again in December of 2014.

This same process is believed to be responsible for a new fracture that was identified from OSIRIS images taken in June 2016. This 150-300 meter-long (492 – 984 ft) fracture appears to have formed parallel to the original. In addition, photographs taken in February of 2015 and June of 2016 (shown above) revealed how a 4 meter-wide (13 ft) boulder that was sitting close to the fractures appeared to have moved by about 15 meters (49 ft).

Whether or not the two phenomena are related is unclear. But it is clear that something very similar appears to have taken place in the Khonsu region. In this section of the comet (which corresponds to one of its larger lobes), images taken between May of 2015 and June 2016 (shown below) revealed how a much larger boulder appeared to have moved even farther between the two time periods.

Images showing a moving boulder in the Khonsu region. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

This boulder – which measures some 30 meters (98 ft) across and weighs an estimated 12,800 metric tonnes (~14,100 US tons) – moved a distance of about 140 meters (~460 ft). In this case, outgassing during perihelion is believed to be the culprit. On the one hand, it could have caused the surface material to erode beneath it (thus causing it to roll downslope) or by forcibly pushing it.

For some time, it has been known that comets undergo changes during the course of their orbits. Thanks to the Rosetta mission, scientists have been able to see these processes in action for the first time. Much like all space probes, vital information continues to be discovered long after the Rosetta mission officially came to an end. Who knows what else the probe managed to witness during its historic mission, and which we will be privy to?

Further Reading: ESA

Here’s Something We Never Thought We’d See on a Comet: Shifting Dunes

The Rosetta mission’s close-up views of the curiously-shaped Comet 67P/Churyumov-Gerasimenko have already changed some long-held ideas about comets. But here’s more: there’s a ‘wind’ blowing across the comet’s surface, creating moving shifting dunes.

“The approach to comet 67P/Churyumov–Gerasimenko by the spacecraft Rosetta has revealed the presence of astonishing dune-like patterns,” wrote Philippe Claudin, of the Institute of Industrial Physics and Chemistry, Paris, France, in his new paper, noting the unusual and unexpected conditions found on Comet 67P.

Left, an image of comet Chury showing outgassing of water vapor, which entrains dust (© ESA/Rosetta/NAVCAM). Right, the neck region, between the comet’s two lobes. Various types of relief can be seen, including the dunes, at bottom left (circled in red), in the sandy region. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA).

Images from Rosetta’s cameras revealed the dusty covering of the comet may be several meters thick in places, which was surprising. But even more surprising was seeing active dunes that are changing. The dunes were seen on both of the ‘lobes’ of the comet as well as on the neck that connects them. Comparisons images taken 16 months of the same region shows evidence that the dunes moved, and are therefore active.

Claudin and his team said that the formation of sedimentary dunes requires the presence of grains and of winds that are strong enough to transport them along the ground. However, comets do not have a dense, permanent and active atmosphere like Earth does. Also, Comet 67P’s gravity is so weak – only about 1/50,000 that of Earth’s – that fast moving grains might be ‘launched’ into space.

What could be creating a wind strong enough that not only moved the grains, but also some boulders up to a meter wide?

There is indeed a wind blowing along the comet’s surface, said Claudin, coming from gases that escape from the surface.
Gases escape at ‘sunset’ on the comet, caused by the pressure difference between the sunlit side, where the surface ice can sublimate due to the energy provided by the sunlight, and the night side.

“This transient atmosphere is still extremely tenuous, with a maximum pressure at perihelion, when the comet is closest to the Sun, 100,000 times lower than on Earth,” the team said in a press release. “However, gravity on the comet is also very weak, and an analysis of the forces exerted on the grains at the comet’s surface shows that these thermal winds can transport centimeter-scale grains, whose presence has been confirmed by images of the ground. The conditions required to allow the formation of dunes, namely winds able to transport the grains along the ground, are thus met on Chury’s surface.”

Summary of properties of Comet 67P/Churyumov–Gerasimenko, as determined by Rosetta’s instruments during the first few months of its comet encounter. Credit: ESA.

The transportation of dust has created dune-like ripples, and boulders with ‘wind-tails’ – the boulders act as natural obstacles to the direction of the gas flow, creating streaks of material ‘downwind’ of them.

Claudin said this finding represents a step forward in understanding the various processes at work on cometary surfaces, and also shows the Rosetta mission still has many surprises and discoveries in store.

Paper: Giant ripples on comet 67P/Churyumov–Gerasimenko sculpted by sunset thermal wind

Press release

Here Are the Last Images We’ll Ever See From Rosetta

The Rosetta team has released the final batch of images taken by the NAVCAM during the last month of its two years of investigations at Comet 67P/Churyumov-Gerasimenko. It’s a big batch and they are absolutely stunning, but its sad to know they are the last NAVCAM images. The image set covers the period from September 2-30, 2016 when the spacecraft was on elliptical orbits that sometimes brought it to within 2 km of the comet’s surface, so you’ll see a wide variety of imagery with a variety of geology and lighting conditions.

Take a look below:

A large boulder sits precariously on Comet 67P/Churyumov-Gerasimenko as seem by Rosetta's NAVCAM on September 11, 2016. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.
A large boulder sits precariously on Comet 67P/Churyumov-Gerasimenko as seem by Rosetta’s NAVCAM on September 11, 2016. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.

While these are the final NAVCAM images, there may be more images coming from the OSIRIS camera. Also, many other instruments will be releasing data, as they were active as long as possible before impact. Many of the science instruments were expected to return their last data from between 20 meters to 5 meters above the surface.

ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) collected data on the density of gas around the comet and its composition while GIADA (Grain Impact Analyser and Dust Accumulator) measured the dust density.

RPC’s (Rosetta Plasma Consortium) instrument suite provided a look at interaction between the solar wind and the surface of the comet. Alice, an Ultraviolet Imaging Spectrometer similar to the one on New Horizons, took high resolution ultraviolet spectra of the surface. RSI (Radio Science Investigation) got the most accurate measurements of the gravity field during descent.

A variety of geology and light on on Comet 67P/Churyumov-Gerasimenko as seem by Rosetta's NAVCAM on September 5, 2016. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.
A variety of geology and light on on Comet 67P/Churyumov-Gerasimenko as seem by Rosetta’s NAVCAM on September 5, 2016. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.
A field of bright bolders on Comet 67P/Churyumov-Gerasimenko as seem by Rosetta's NAVCAM during September 2-20. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.
A field of bright bolders on Comet 67P/Churyumov-Gerasimenko as seem by Rosetta’s NAVCAM during September 2-20. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.

And here’s one of the last five images from Rosetta’s NAVCAM as it descended to its controlled impact on September 30 onto Comet 67P, taking incredible, close-up images during descent, this one just 18.1 km up. It shows the “drippy icing” landscape on this portion of the comet:

Single frame enhanced NavCam image taken on September 30, 2016 at 00:27 GMT, when Rosetta was 18.1 km from the center of the nucleus of Comet 67P/Churyumov-Gerasimenko. The scale at the surface is about 1.5 m/pixel and the image measures about 1.6 km across. ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.
Single frame enhanced NavCam image taken on September 30, 2016 at 00:27 GMT, when Rosetta was 18.1 km from the center of the nucleus of Comet 67P/Churyumov-Gerasimenko. The scale at the surface is about 1.5 m/pixel and the image measures about 1.6 km across. ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.

You can see all the final images at the Rosetta blog.

Journey’s End: Comet Crash for Rosetta Mission Finale

With a soft “awwww” from the mission team in the control center in Darmstadt, Germany, the signal from the Rosetta spacecraft faded, indicating the end of its journey. Rosetta made a controlled impact onto Comet 67P/Churyumov–Gerasimenko, sending back incredible close-up images during descent, after two years of investigations at the comet.

“Farewell Rosetta. You have done the job. That was space science at its best,” said Patrick Martin, Rosetta mission manager.

Rosetta’s final resting spot appears to be in a region of active pits in the Ma’at region on the two-lobed, duck-shaped comet.

The information collected during the descent – as well as during the entire mission – will be studied for years. So even though the video below about the mission’s end will likely bring a tear to your eye, rest assured the mission will continue as the science from Rosetta is just getting started.

“Rosetta has entered the history books once again,” says Johann-Dietrich Wörner, ESA’s Director General. “Today we celebrate the success of a game-changing mission, one that has surpassed all our dreams and expectations, and one that continues ESA’s legacy of ‘firsts’ at comets.”

Launched in 2004, Rosetta traveled nearly 8 billion kilometers and its journey included three Earth flybys and one at Mars, and two asteroid encounters. It arrived at the comet in August 2014 after being in hibernation for 31 months.

After becoming the first spacecraft to orbit a comet, it deployed the Philae lander in November 2014. Philae sent back data for a few days before succumbing to a power loss after it unfortunately landed in a crevice and its solar panels couldn’t receive sunlight. But Rosetta continued to monitor the comet’s evolution as it made its closest approach and then moved away from the Sun. However, now Rosetta and the comet are too far away from the Sun for the spacecraft to receive enough power to continue operations.

“We’ve operated in the harsh environment of the comet for 786 days, made a number of dramatic flybys close to its surface, survived several unexpected outbursts from the comet, and recovered from two spacecraft ‘safe modes’,” said operations manager Sylvain Lodiot. “The operations in this final phase have challenged us more than ever before, but it’s a fitting end to Rosetta’s incredible adventure to follow its lander down to the comet.”

Compilation of the brightest outbursts seen at Comet 67P/Churyumov–Gerasimenko by Rosetta’s OSIRIS narrow-angle camera and Navigation Camera between July and September 2015. Credit: OSIRIS: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; NavCam: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0.
Compilation of the brightest outbursts seen at Comet 67P/Churyumov–Gerasimenko by Rosetta’s OSIRIS narrow-angle camera and Navigation Camera between July and September 2015. Credit: OSIRIS: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; NavCam: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0.

Rosetta’s Legacy and Discoveries

Of its many discoveries, Rosetta’s close-up views of the curiously-shaped Comet 67P have already changed some long-held ideas about comets. With the discovery of water with a different ‘flavor’ to that of Earth’s oceans, it appears that Earth impacts of comets like 67P/Churyumov–Gerasimenko may not have delivered as much of Earth’s water as previously thought.

From Philae, it was determined that even though organic molecules exist on the comet, they might not be the kind that can deliver the chemical prerequisites for life. However, a later study revealed that complex organic molecules exist in the dust surrounding the comet, such as the amino acid glycine, which is commonly found in proteins, and phosphorus, a key component of DNA and cell membranes. This reinforces the idea that the basic building blocks may have been delivered to Earth from an early bombardment of comets.

Rosetta’s long-term monitoring has also shown just how important the comet’s shape is in influencing its seasons, in moving dust across its surface, and in explaining the variations measured in the density and composition of the comet’s coma.

And because of Rosetta’s proximity to the comet, we all went along for the ride as the spacecraft captured views of what happens as a comet comes close to the Sun, with ice sublimating and dusty jets exploding from the surface.

Studies of the comet show it formed in a very cold region of the protoplanetary nebula when the Solar System was forming more than 4.5 billion years ago. The comet’s two lobes likely formed independently, but came together later in a low-speed collision.

“Just as the Rosetta Stone after which this mission was named was pivotal in understanding ancient language and history, the vast treasure trove of Rosetta spacecraft data is changing our view on how comets and the Solar System formed,” said project scientist Matt Taylor.

Sequence of images captured by Rosetta during its descent to the surface of Comet 67P/C-G on September 30, 2016. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.
Sequence of images captured by Rosetta during its descent to the surface of Comet 67P/C-G on September 30, 2016. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

Journey’s End

During the final hours of the mission on Friday morning, the instrument teams watched the data stream in and followed the spacecraft as it moved closer to its targeted touchdown location on the “head” of the 4km-wide comet. The pitted region where Rosetta landed appear to be the places where 67P ejects gas and dust into space, and so Rosetta’s swan song will provide more insight into the comet’s icy jets.

“With the decision to take Rosetta down to the comet’s surface, we boosted the scientific return of the mission through this last, once-in-a-lifetime operation,” said Martin. ““It’s a bittersweet ending, but … Rosetta’s destiny was set a long time ago. But its superb achievements will now remain for posterity and be used by the next generation of young scientists and engineers around the world.”

See more stunning, final images in Bob King’s compilation article, and we bid Rosetta farewell with this lovely poem written by astropoet Stuart Atkinson (used here by permission).

Rosetta’s Last Letter Home

By Stuart Atkinson

And so, my final day dawns.
Just a few grains are left to drain through
The hourglass of my life.
The Comet is a hole in the sky.
Rolling, turning, a black void churning
Silently beneath me.
Down there, waiting for me, Philae sleeps,
Its bed a cold cave floor,
A quilt of sparkling hoarfrost
Pulled over its head…

I have so little time left;
I sense Death flying behind me,
I feel his breath on my back as I look down
At Ma’at, its pits as black as tar,
A skulls’s empty eye sockets staring back
At me, daring me to leave the safety
Of this dusty sky and fly down to join them,
Never to spread my wings again; never
To soar over The Comet’s tortured pinnacles and peaks,
Or play hide and seek in its jets and plumes…

I don’t want to go.
I don’t want to be buried beneath that filthy snow.
This is wrong! I want to fly on!
There is so much more for me to see,
So much more to do –
But the end is coming soon.
All I ask of you is this: don’t let me crash.
Help me land softly, kissing the ground,
Coming to rest with barely a sound
Like a leaf falling from a tree.
Don’t let me die cartwheeling across the plain,
Wings snapping, cameras shattering,
Pieces of me scattering like shrapnel
Across the ice. Let me end my mayfly life
In peace, whole, not as debris rolling uncontrollably
Into Deir el-Medina…

It’s time to go, I know.
Only hours remain until I join Philae
And my great adventure ends
So I’ll send this and say goodbye.
If I dream, I’ll dream of Earth
Turning beneath me, bathing me in
Fifty shades of blue…
In years to come I hope you’ll think of me
And smile, remembering how, for just a while,
We explored a wonderland of ice and dust
Together, hand in hand.

(c) Stuart Atkinson 2016

Rosetta Wows With Amazing Closeups of Comet 67P Before Final ‘Crunchdown’

Landscape on Comet 67P taken from just 10 miles (16 km) up late Thursday evening during Rosetta's free fall . The image measures 2,014 feet (614 meters) across or just under a half-mile. At typical walking speed, you could walk from one end to the other in 10 minutes. Credit: ESA/Rosetta
Craggy hills meet dust-covered plains in this landscape on Comet 67P taken from 10 miles (16 km) up late Thursday evening during Rosetta’s free fall . The image measures 2,014 feet (614 meters) across or just under a half-mile. At typical walking speed, you could walk from one side to the other in 10 minutes. This and all the photos below are copyright ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Rosetta fell silent moments after 6:19 a.m. Eastern Time (12:19 UT) this morning, when it gently crashed into 67P/C-G 446 million miles (718 million km) from Earth. As the probe descended to the comet’s bouldery surface of the comet in free fall, it snapped a series of ever-more-detailed photographs while gathering the last bits data on the density and composition of cometary gases, surface temperature and gravity field before the final curtain was drawn.

Let’s take the trip down, shall we?

Rosetta's last navigation camera image was taken just after the collision maneuver sequence Thursday evening (CDT) when the probe was 9.56 miles (15.4 km) above the comet's surface. Credit: ESA/Rosetta
Rosetta’s last navigation camera image was taken just after the collision maneuver sequence Thursday evening (CDT) when the probe was 9.56 miles (15.4 km) above the comet’s surface. As in the photo above, much of the landscape is coated in a thick layer of dust that smoothes the comet’s contours.
As Rosetta continues its descent onto the Ma'at region on the small lobe of Comet 67P/Churyumov-Gerasimenko, the OSIRIS narrow-angle camera captured this image at 08:18 GMT from an altitude of about 5.8 km. The image shows dust-covered terrains, exposed walls and a few boulders on Ma'at, not far from the target impact region (not visible in this view - located below the lower edge).Copyright ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
As Rosetta continued its descent onto the Ma’at region on the small lobe of Comet 67P/Churyumov-Gerasimenko, the OSIRIS narrow-angle camera captured this photo from 3.6 miles (5.8 km) up. We see dust-covered terrains, exposed walls and a few boulders on Ma’at, not far from the target impact region, which is located just below the lower edge. The image measures 738 feet (225 meters) across.
Comet from 5.7 km. Rosetta’s OSIRIS narrow-angle camera captured this image of Comet 67P/Churyumov-Gerasimenko at 08:21 GMT during the spacecraft’s final descent on September 30, 2016. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Just a little bit lower now. This photo showing dramatic shadows was taken from 3.5 miles (5.7 km) above the surface of the comet at 4:21 a.m. EDT Friday morning September 30.
It looks like the probe's headed for the abyss! This photo was made at 6:14 a.m. just minutes before impact from 3/4 mile (1.2 km) high. The scene measures just 33 meters across.
Headed for the abyss? This photo was made at 6:14 a.m. from 3/4 mile (1.2 km) high just a few minutes before impact. The scene measures just 108 feet (33 meters) wide.
This is Rosetta's last image of Comet 67P/Churyumov-Gerasimenko, taken shortly before impact, an estimated 51 m above the surface.
This is Rosetta’s final image of Comet 67P/Churyumov-Gerasimenko, taken shortly before impact, an estimated 66 feet (~20 meters) above the surface. The view is similar to looking down from atop a three-story building. Side to side, the photo depicts an area only 7.8 feet (2.4 meters) across. The image is soft because Rosetta’s cameras weren’t designed to photograph the comet from this close.
Sad to see its signal fade. Going... going... gone! A sequence of screenshots showing the signal from Rosetta seen at ESA's ESOC mission control centre via NASA's 70m tracking station at Madrid during comet landing on 30 September 2016. The peak of the spectrum analyser is strong at 12:19 CEST, and a few moments later, it's gone. Credit: ESA
Sad to see its signal fade. A sequence of screenshots taken at ESA’s ESOC mission control show the signal from Rosetta fading moments before impact. The peak of the spectrum analyser is strong at 6:19 EDT, and a few moments later, it’s gone. At impact, Rosetta’s was shut down and no further communication will or can be made with the spacecraft. It will continue to rest on the comet for well-nigh eternity until 67P vaporizes and crumbles apart. Credit: ESA

Goodbye Forever Philae; We Hardly Knew Ye

You can’t say they didn’t try, but the news is sad nonetheless. ESA announced the mission for the Philae lander – the first spacecraft to ever land on a comet — is officially over. The system that enables communications between the Rosetta spacecraft and Philae – which sitting in a shaded region on Comet 67P/Churyumov-Gerasimenko – is being switched off on July 27, 2016, at 09:00 UTC.

“It’s time for me to say goodbye,” Philae tweeted on Tuesday. “Tomorrow, the unit on @ESA_Rosetta for communication with me will be switched off forever…”

Philae has mostly been in hibernation after its dramatic touchdown (actually, three or maybe four touchdowns) on Nov. 12, 2014 when it separated from the orbiting Rosetta spacecraft, flew, landed, bounced and then repeated that process for more than two hours across the surface. The harpoons that were to anchor Philae to the surface failed to fire, and scientists estimated the lander may have bounced as high as 3.2 kilometers (2 miles) before becoming wedged in the shadows of a cliff on the odd-shaped comet. The solar-powered lander quickly ran out of power, just hours after landing. Philae’s final location has been plotted but never actually seen by Rosetta.

Slow animation of images taken by Philae’s Rosetta Lander Imaging System, ROLIS, trace the lander’s descent to the first landing site, Agilkia, on Comet 67P/Churyumov–Gerasimenko on November 12, 2014. Credits: ESA/Rosetta/Philae/ROLIS/DLR
Slow animation of images taken by Philae’s Rosetta Lander Imaging System, ROLIS, trace the lander’s descent to the first landing site, Agilkia, on Comet 67P/Churyumov–Gerasimenko on November 12, 2014.
Credits: ESA/Rosetta/Philae/ROLIS/DLR

After months of silence, the team heard briefly from Philae on June 13, 2015, when it transmitted information on its power and computer subsystems. It then made seven intermittent contacts with Rosetta in the following weeks, with the last coming on July 9, but the communications were too short and unstable to transmit or receive any meaningful scientific or engineering data.

Since then, the Support System Processor Unit (ESS) on Rosetta was kept on in the unlikely chance that Philae would wake up and try to reestablish contact. The hope was that when the comet was closer to the Sun, it might receive enough light to power up.

But the reason for turning it off now is due to Rosetta’s own impending end of mission, coming on September 30, 2016 when it will make a controlled impact at the Ma’at region on the comet’s “head.” Emily Lakdawalla of The Planetary Society put together this annotated image of sites where Philae touched down and likely landed, and where Rosetta will end up:

The 19 regions identified on Comet 67P/Churyumov–Gerasimenko are separated by distinct geomorphological boundaries. Following the ancient Egyptian theme of the Rosetta mission, they are named for Egyptian deities. They are grouped according to the type of terrain dominant within each region. Five basic categories of terrain type have been determined: dust-covered (Ma’at, Ash and Babi); brittle materials with pits and circular structures (Seth); large-scale depressions (Hatmehit, Nut and Aten); smooth terrains (Hapi, Imhotep and Anubis), and exposed, more consolidated (‘rock-like’) surfaces (Maftet, Bastet, Serqet, Hathor, Anuket, Khepry, Aker, Atum and Apis). All three landing sites (Philae initial and final sites and the planned resting place of the Rosetta orbiter) are located on the northern part of the "head" of the comet. Base map: ESA / Rosetta / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA. Landing site locations: Emily Lakdawalla.
The 19 regions identified on Comet 67P/Churyumov–Gerasimenko are separated by distinct geomorphological boundaries. Following the ancient Egyptian theme of the Rosetta mission, they are named for Egyptian deities. They are grouped according to the type of terrain dominant within each region. Five basic categories of terrain type have been determined: dust-covered (Ma’at, Ash and Babi); brittle materials with pits and circular structures (Seth); large-scale depressions (Hatmehit, Nut and Aten); smooth terrains (Hapi, Imhotep and Anubis), and exposed, more consolidated (‘rock-like’) surfaces (Maftet, Bastet, Serqet, Hathor, Anuket, Khepry, Aker, Atum and Apis). All three landing sites (Philae initial and final sites and the planned resting place of the Rosetta orbiter) are located on the northern part of the “head” of the comet.
Base map: ESA / Rosetta / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA. Landing site locations: Emily Lakdawalla.

The team decided to keep “Rosetta’s listening channel on until it is no longer possible due to power constraints as we move ever further from the Sun towards the end of the mission,” said Patrick Martin, ESA’s Rosetta mission manager.

Martin said that by the end of this week, the spacecraft will be about 520 million km from the Sun, and will start facing a significant loss of power – about 4W per day. In order to continue scientific operations over the next two months and to maximize their return, it became necessary to start reducing the power consumed by the non-essential payload components on board.

But, Martin added that the mission of Philae and Rosetta will always be remembered as an incredible success.

“The combined achievements of Rosetta and Philae, rendezvousing with and landing on a comet, are historic high points in space exploration,” he said.

Philae did achieve 80% of its primary science goals in its short 64-hour active mission, as it took detailed images of the comet from above and on the surface, searched for organic compounds, and profiled the local environment and surface properties of the comet, “providing revolutionary insights into this fascinating world,” ESA said.

Sources: ESA, The Planetary Society, ESA blog

Spectacular Celestial Fireworks Commemorate Perihelion Passage of Rosetta’s Comet

Sequence of OSIRIS narrow-angle camera images from 12 August 2015, just a few hours before the comet reached perihelion. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
See hi res images below[/caption]

A spectacular display of celestial fireworks like none ever witnessed before, burst forth from Rosetta’s comet right on time – commemorating the Europeans spacecraft’s history making perihelion passage after a year long wait of mounting excitement and breathtaking science.

As the European Space Agency’s (ESA’s) Rosetta marked its closest approach to the Sun (perihelion) at exactly 02:03 GMT on Thursday, August 13, 2015, while orbiting Comet 67P/Churyumov–Gerasimenko, its suite of 11 state-of-the-art science instruments, cameras and spectrometers were trained on the utterly bizarre bi-lobed body to capture every facet of the comet’s nature and environment for analysis by the gushing science teams.

And the perihelion passage did not disappoint – living up to its advance billing by spewing forth an unmatched display of otherworldly outbursts of gas jets and dust particles due to surface heating from the warming effects of the sun as the comet edged ever closer, coming within 186 million kilometers of mighty Sol.

ESA has released a brand new series of images, shown above and below, documenting sparks flying – as seen by Rosetta’s OSIRIS narrow-angle camera and NAVCAM wider angle cameras on August 12 and 13 – just a few hours before the rubby ducky shaped comet reached perihelion along its 6.5-year orbit around the sun.

Images of Comet 67P/C-G taken with OSIRIS narrow-angle camera on 12 August 2015, just a few hours before the comet reached perihelion, about 330 km from the comet. The individual images are also available below. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Images of Comet 67P/C-G taken with OSIRIS narrow-angle camera on 12 August 2015, just a few hours before the comet reached perihelion, about 330 km from the comet. The individual images are also available below. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Indeed the navcam camera image below was taken just an hour before the moment of perihelion, at 01:04 GMT, from a distance of around 327 kilometers!

Frozen ices are seen blasting away from the comet in a hail of gas and dust particles as rising solar radiation heats the nucleus and fortifies the comet’s atmosphere, or coma, and its tail.

Comet at perihelion.  Single frame Rosetta navigation camera image acquired at 01:04 GMT on 13 August 2015, just one hour before Comet 67P/Churyumov–Gerasimenko reached perihelion – the closest point to the Sun along its 6.5-year orbit. The image was taken around 327 km from the comet. It has a resolution of 28 m/pixel, measures 28.6 km across and was processed to bring out the details of the comet's activity. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
Comet at perihelion. Single frame Rosetta navigation camera image acquired at 01:04 GMT on 13 August 2015, just one hour before Comet 67P/Churyumov–Gerasimenko reached perihelion – the closest point to the Sun along its 6.5-year orbit. The image was taken around 327 km from the comet. It has a resolution of 28 m/pixel, measures 28.6 km across and was processed to bring out the details of the comet’s activity. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

After a decade long chase of over 6.4 billion kilometers (4 Billion miles), ESA’s Rosetta spacecraft arrived at the pockmarked Comet 67P/Churyumov-Gerasimenko exactly a year ago on Aug. 6, 2014 for history’s first ever attempt to orbit a comet for long term study.

In the interim, Rosetta also deployed the piggybacked Philae lander for history’s first landing on a comet on Nov. 12, 2014.

In fact, measurements from Rosetta’s science instruments confirm the comet is belching a thousand times more water vapor today than was observed during Rosetta’s arrival a year ago. It’s spewing some 300 kg of water vapour every second now, compared to just 300 g per second upon arrival. That equates to two bathtubs per second now in Aug. 2015 vs. two small glasses of water per second in Aug. 2014.

Besides gas, 1000 kg of dust per second is simultaneously erupting from the nucleus, “creating dangerous working conditions for Rosetta,” says ESA.

“In recent days, we have been forced to move even further away from the comet. We’re currently at a distance of between 325 km and 340 km this week, in a region where Rosetta’s startrackers can operate without being confused by excessive dust levels – without them working properly, Rosetta can’t position itself in space,” comments Sylvain Lodiot, ESA’s spacecraft operations manager, in an ESA statement.

Here’s an OSIRIS image taken just hours prior to perihelion, that’s included in the lead animation of this story.

OSIRIS NAC image of Comet 67P/C-G taken on 12 August 2015 at 17:35 GMT. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
OSIRIS NAC image of Comet 67P/C-G taken on 12 August 2015 at 17:35 GMT. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The period of the comet’s peak intensity, as seen in all these images, is expected to continue past perihelion for several weeks at least and fulfils the dreams of a scientific goldmine for all the research teams and hundreds of researchers involved with Rosetta and Philae.

“Activity will remain high like this for many weeks, and we’re certainly looking forward to seeing how many more jets and outburst events we catch in the act, as we have already witnessed in the last few weeks,” says Nicolas Altobelli, acting Rosetta project scientist.

And Rosetta still has lots of fuel, and just as important – funding – to plus up its ground breaking science discoveries.

ESA recently granted Rosetta a 9 month mission extension to continue its research activities as well as having been given the chance to accomplish one final and daring historic challenge.

Engineers will attempt to boldly go and land the probe on the undulating surface of the comet.

Officials with the European Space Agency (ESA) gave the “GO” on June 23 saying “The adventure continues” for Rosetta to march forward with mission operations until the end of September 2016.

If all continues to go well “the spacecraft will most likely be landed on the surface of Comet 67P/Churyumov-Gerasimenko” said ESA.

ESA Philae lander approaches comet 67P/Churyumov–Gerasimenko on 12 November 2014 as imaged from Rosetta orbiter after deployment and during seven hour long approach for 1st ever  touchdown on a comets surface.  Credit:  ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA - Composition by Marco Di Lorenzo/Ken Kremer
ESA Philae lander approaches comet 67P/Churyumov–Gerasimenko on 12 November 2014 as imaged from Rosetta orbiter after deployment and during seven hour long approach for 1st ever touchdown on a comets surface. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA – Composition by Marco Di Lorenzo/Ken Kremer

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

Jets of gas and dust are blasting from the active neck of comet 67P/Churyumov-Gerasimenko in this photo mosaic assembled from four images taken on 26 September 2014 by the European Space Agency’s Rosetta spacecraft at a distance of 26.3 kilometers (16 miles) from the center of the comet. Credit: ESA/Rosetta/NAVCAM/Marco Di Lorenzo/Ken Kremer/kenkremer.com
Jets of gas and dust are blasting from the active neck of comet 67P/Churyumov-Gerasimenko in this photo mosaic assembled from four images taken on 26 September 2014 by the European Space Agency’s Rosetta spacecraft at a distance of 26.3 kilometers (16 miles) from the center of the comet. Credit: ESA/Rosetta/NAVCAM/Marco Di Lorenzo/Ken Kremer/kenkremer.com

Why is it Tough to Land on a Comet?

Why is landing on a comet so difficult and what does this tell us about future missions to comets and asteroids?

Us nerds were riveted by the coverage of the ESA’s Rosetta mission and its arrival at Comet 67/P in 2014. One such nerd is Paco Juarez, friend of the show and patron. He wanted to know why is it so darned hard to land on a comet?

In 2014, the tiny Philae Lander detached from the spacecraft and slowly descended down to the surface of the comet. If everything went well, it would have gracefully touched down and then sent back a pile of information about this filthy roving snowball.
As you know, the landing didn’t go according to plan. Instead of gently touching down on 67/P, Philae bounced off the surface of the comet like a tennis ball dropped from a tower, and rose a kilometer off the surface. Then more descending, and more bouncing, finally settling down on rugged terrain, surrounded by crevices and large boulders. At that point, engineers lost contact with the lander, and so much science went undone.

If I recorded this video a few months ago, that would have been the end of the story. You know how this goes, space exploration is hard and dangerous, don’t be surprised when your missions fail and space unfeelingly smashes up your pretty little robot probes with their little gold foil 27 pieces of flair.

Rosetta
Rosetta

Fortunately, I’m able to report that ESA regained contact with the Philae lander on June 13, 2015, resuming its mission, and scientific operations.

But why is landing on a comet so difficult and what does this tell us about future robotic and human missions to smaller comets and asteroids? When ESA engineers designed Philae, they knew it was going to be very difficult to land on a comet like 67/P because they have a such a low gravity. And they have low gravity because they’re little.

Illustration of the Rosetta Missions Philae lander on final approach to a comet surface. (Photo: ESA)
Illustration of the Rosetta Missions Philae lander on final approach to a comet surface. (Photo: ESA)

On Earth, 6 septillion tonnes of rock and metal give you an escape velocity of 11.2 km/s. That’s how fast you need to be able to jump in order to leave the planet entirely. But the escape velocity of 67/P is only 1 m/s. You could trip off the comet and never return. Whilst small children threw rocks at you from the surface as you drifted away.

Philae was built with harpoon drills in its landing struts. The moment the lander touched the surface of the comet, those harpoons were supposed to fire, securing the lander. The surface of the comet was softer than scientists had anticipated, and the harpoons didn’t fire. Or possibly they were broken and couldn’t fire. Space is hard. Whatever the case, without being able to grab onto the surface, it used the comet as a bouncy castle.

We’re learning what it takes to land on lower mass objects like comets and asteroids. NASA’s OSIRIS-REx mission will visit Comet Bennu, and send a lander down to the surface of the asteroid. From there it’ll pick up a few samples, and return them back to Earth. It’ll be Philae, all over again.

An artist concept of the Philae lander on comet 67P/Churyumov-Gerasimenko.  Credit: Astrium - E. Viktor/ESA
An artist concept of the Philae lander on comet 67P/Churyumov-Gerasimenko. Credit: Astrium – E. Viktor/ESA

In the future, we’re told, humans will be visiting asteroids to study them for science and their potential for ice and minerals. You can imagine it’ll be a harrowing descent, but even just walking around on the surface will be dangerous when every step could throw an astronaut into an escape trajectory. They’ll need to learn lessons from rock climbers and Rorschach.

As we learned with Philae, landings on low mass objects is really tough. We’re going to need to get more practice and develop new techniques and technologies before we’re ready to add asteroid mining to our list of “stuff we just do, NBD”.

What are some unusual worlds you’d like humanity to visit? Put your suggestions in the comments below.