We’re finally getting to know the icy nucleus behind comet 67P/Churyumov-Gerasimenko. For all the wonder that comets evoke, we on Earth never see directly what whips up the coma and tail. Even professional telescopes can’t burrow through the dust and vapor cloaking the nucleus to distinguish the clear outline of a comet’s heart. The only way to see one is to fly a camera there.
Rosetta took 10 years to reach 67P/C-G, a craggy, boot-shaped body that resembles an asteroid in appearance but with key differences. Asteroids shown in close up photos often display typical bowl-shaped impact craters. From the photos to date, 67P/C-G’s ‘craters’ look shallow and flat in comparison. Were they impacts smoothed by ice flows over time? Did some of the dust and vapor spewed by the comet settle back on the surface to partially bury and soften the landscape?
While 67P is doubtless its own comet, it does share certain similarities with Comet 81P/Wild including at least a few crater-like depressions seen during NASA’s Stardust mission. In January 2004, the spacecraft gathered photos, measurements and dust samples during its brief flyby of the nucleus. Photos reveal pinnacles, flat-bottomed depressions and bright plumes or jets of vaporizing ice.
In a 2004 paper by Donald Brownlee and team, the group experimentally reproduced the flat-floored craters by firing projectiles into resin-coated sand baked a bit to make it cohere. Their results suggest the craters formed from impacts in loosely compacted material under the low-gravity conditions typical of small objects like comets. To quote the paper: “Most disrupted material stayed inside the cavity and formed a flat-floored deposit and steep cliffs formed the rim.” Icy materials mixed with dust may have also played a role in their appearance and other crater-like depressions called pit-halos.
Speculation isn’t science, so I’ll stop here. So much more data will be streaming in soon, we’ll have our hands full. On Wednesday, August 6th, Rosetta will enter orbit around the nucleus and begin detailed studies that will continue through December 2015. Studying the new pictures now arriving daily, I’m struck by the dual nature of comets. We see an ancient landscape and yet one that looks strangely contemporary as the sun vaporizes ice, reworking the terrain like a child molding clay.
ESA’s Rosetta Spacecraft nears final approach to Comet 67P/Churyumov-Gerasimenko in late July 2014. This collage of imagery from Rosetta combines Navcam camera images at right taken nearing final approach from July 25 to July 31, 2014, with OSIRIS wide angle camera image at left of comet’s coma on July 25 from a distance of around 3000 km. On July 31 Rosetta had approached to within 1327 km. Images to scale and contrast enhanced to show further detail. Credit: ESA/Rosetta/NAVCAM/OSIRIS/MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA Collage/Processing: Marco Di Lorenzo/Ken Kremer – kenkremer.com Story updated[/caption]
The European Space Agency’s (ESA) Rosetta spacecraft is at last rapidly closing in on its target destination, Comet 67P/Churyumov-Gerasimenko, after a decade long chase of 6.4 billion kilometers through interplanetary space. See imagery above and below.
As of today, Friday, August 1, ESA reports that Rosetta has approached the ‘rubber ducky looking’ comet to within a distance of less than 1153 kilometers. That distance narrows with each passing moment as the speeding robotic probe moves closer and closer to the comet while looping around the sun at about 55,000 kilometers per hour (kph).
Rosetta is now just 5 days away from becoming Earth’s first probe ever to rendezvous and enter orbit around a comet.
See above our image collage of Rosetta nearing final approach with the spacecrafts most recent daily Navcam camera images, all taken within the past week starting on July 25 and including up to the most recently release image snapped on July 31. The navcam images are all to scale to give the sense of the spacecraft approaching the comet and revealing ever greater detail as it grows in apparent size in the cameras field of view. The navcam images were also taken at about the same time of day each day.
The highest resolution navcam image yet of the two lobed comet – merged at a bright band – was taken on July 31 from a distance of 1327 kilometers and published within the past few hours by ESA today, Aug 1. It shows the best view yet of the surface features of the mysterious bright necked wanderer composed of primordial ice, rock, dust and more.
The Navcam collage is combined with an OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) wide angle camera view of the comet and its asymmetric coma of ice and dust snapped on July 25 from a distance of around 3000 km, and with an exposure time of 300 seconds. The OSIRIS image covers an area of about 150 x 150 km (90 mi x 90 mi). The images have been contrast enhanced to bring out more detail.
Scientists speculate that the comets bright neck region could be caused by differences in material or grain size or topological effects.
Rosetta’s history making orbital feat is slated for Aug. 6 following the final short duration orbit insertion burns on Aug. 3 and Aug. 6 to place Rosetta into orbit at an altitude of about 100 kilometers (62 miles) where it will study and map the 4 kilometer wide comet for some 17 months.
The comet rotates around once every 12.4 hours.
“If any glitches in space or on ground had delayed the most recent burns, orbital mechanics dictate that we’d only have had a matter of a few days to fix the problem, re-plan the burn and carry it out, otherwise we run the risk of missing the comet,” says Trevor Morley, a flight dynamics specialist at ESOC.
In November 2014 the Rosetta mothership will deploy the Philae science lander for the first ever attempt to land on a comet’s nucleus using harpoons to anchor itself to the surface while the comet is rotating.
As Rosetta edges closer on its final lap, engineers at mission control at the European Space Operations Centre (ESOC), in Darmstadt, Germany have commanded the probes navigation camera (navcam) to capture daily images while the other science instruments also collect measurements analyzing the comets physical characteristics and chemical composition in detail.
The probe has already discovered that the comet’s surface temperature is surprisingly warm at –70ºC, which is some 20–30ºC warmer than predicted. This indicates the surface is too hot to be covered in ice and must instead have a dark, dusty crust, says ESA.
Comet 67P/Churyumov-Gerasimenko is a short period comet some 555 million kilometres from the Sun at this time, about three times further away than Earth and located between the orbits of Jupiter and Mars.
You can watch the Aug. 6 orbital arrival live via a livestream transmission from ESA’s spacecraft operations centre in Darmstadt, Germany.
While you were reading this the gap between the comet and Rosetta closed to less than 1000 kilometers!
Stay tuned here for Ken’s continuing Curiosity, Opportunity, Orion, SpaceX, Boeing, Orbital Sciences, commercial space, MAVEN, MOM, Mars and more Earth and Planetary science and human spaceflight news.
Anyone eager for a comet countdown? It’s just a few days now until the Rosetta spacecraft arrives near Comet 67P/Churyumov–Gerasimenko on August 6, and with each passing day more detail becomes visible.
The “rubber duckie”-shaped comet has an average surface temperature of –70 degrees Celsius (-94 degrees Fahrenheit), which is far warmer than scientists expect. At 20 to 30 degrees Celsius (68 to 86 degrees Fahrenheit) warmer than predicted, the scientists say that the comet is too hot to be covered in ice. It must instead of a dark crust.
“This result is very interesting, since it gives us the first clues on the composition and physical properties of the comet’s surface,” stated Fabrizio Capaccioni, principal investigator of the visible, infrared and thermal imaging spectrometer (VIRTIS) that took the measurements.
Capaccioni, who is from Italy’s INAF-IAPS, led a team that took measurements of the comet between July 13 and July 21. What they found was also consistent with the findings from other close-up views of comets, such as 1P/Halley. Observations from afar already revealed that Rosetta had low reflectivity, so this is consistent with those far-off looks.
“This doesn’t exclude the presence of patches of relatively clean ice, however, and very soon, VIRTIS will be able to start generating maps showing the temperature of individual features,” stated Capaccioni.
WOW! We’re really getting to the good stuff now! This is no computer-generated shape model, this is the real deal: the double-lobed nucleus of Comet 67P/C-G, as imaged by Rosetta’s OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) narrow-angle camera on Tuesday, July 29. At the time just about a week away from making its arrival, ESA’s spacecraft was 1,950 km (1,211 miles) from the comet when this image was taken. (That’s about the distance between Providence, Rhode Island and Miami, Florida… that’s one fancy zoom lens, Rosetta!)
This latest image reveals some actual surface features of the 4-km-wide comet, from a few troughs and mounds to the previously-noted bright band around the “neck” connecting the two lobes. The resolution in the July 29 OSIRIS image is 37 meters per pixel.
Since Rosetta is quickly closing the gap between itself and the comet we can only expect better images to come in the days ahead, so stay tuned — this is going to be an exciting August!
…and that time is now! ESA’s Rosetta spacecraft is just over a mere two weeks away from its arrival at Comet 67P/Churyumov-Gerasimenko (which has recently surprised everyone with its binary “rubber duckie” shape) and the excitement continues to grow — and rightfully so, since after ten years traveling through the Solar System Rosetta is finally going to achieve its goal of being the first spacecraft to orbit a comet!
As part of the “Are We There Yet” campaign to encourage public participation in this historic space exploration event, ESA has released the next installment of Rosetta’s story in adorable animated format. Check it out above, and feel free to fall in love with a solar-powered spacecraft.
Keep up with Rosetta’s journey on the ESA website here, and enter the #RosettaAreWeThereYet contest by sharing your photos here (you could win a trip to ESA’s Operations Center in Darmstadt, Germany in November for Philae’s landing party!)
I thought the photos earlier this week were amazing. This little movie, made of 36 ‘smoothed’ or interpolated images of Comet 67P/Churyumov-Gerasimenko, takes it to the next level, showing the comet’s complex shape even more clearly as Rosetta nudges ever closer to its target. Some have likened it to a duck, a boot and even a baby’s foot. The original photos used for the animation were more pixelated, but a technique known as “sub-sampling by interpolation” was used to smooth out the pixels for a more natural look. Be aware that because of processing, 67P C-G appears smoother than it might be. While the surface looks textured, including what appears to be a small crater atop the duck’s head, we have to be careful at this stage not to over-interpret – some of the details are artifacts.
No one knows yet how such an unusual shape formed in the first place. Possibly the comet is a ‘contact binary’ made of two separate comets or two parts of larger, shattered comet that stuck together during a low-velocity collision. This may have happened more 4 billion years ago when the icy building blocks of the planets and comets were numerous and collisions far more frequent than they are today. Contact binaries aren’t uncommon; we see them in asteroids and comets alike.
* The comet may have once been a more spherical object but after many trips around the sun developed an asymmetrical shape from ice vaporization and outgassing.
* A near-catastrophic impact blasted away a huge chunk of comet ice.
* The strong gravitational pull experienced during a close pass of a large planet like Jupiter or Saturn may have pulled it into an irregular shape.
* A large outburst could have weakened a region on the comet’s surface that later crumbled away.
“We will need to perform detailed analyses and modelling of the shape of the comet to determine how best we can fly around such a uniquely shaped body, taking into account flight control and astrodynamics, the science requirements of the mission, and the landing-related elements like landing site analysis and lander-to-orbiter visibility,” said Rosetta Mission Manager Fred Jansen. ” But with fewer than 10,000 km to go before the August 6th rendezvous, our open questions will soon be answered.”
In the meantime, keep the photos and movies coming. We can’t get enough.
A view of Comet 67P/Churyumov-Gerasimenko’s nucleus, appearing to show a double binary. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
It appears that Rosetta’s comet has a double nucleus. A video from the spacecraft speeding towards Comet 67P/Churyumov-Gerasimenko shows what looks two lobes touching each other, which could send a small wrinkle in the plans to land Philae on the comet’s surface later this year.
Edit, July 17: As the original video was removed off of YouTube, we have now replaced it with a GIF of the comet from here.
“The nucleus of the comet is clearly a contact binary — two smaller (and unequally sized object) in close contact,” she wrote, adding the nucleus measures 4 kilometers by 3.5 kilometers (2.5 miles by 2.17 miles).
It has a rotational period of about 12.4 hours.
“Philippe Lamy is quoted as estimating that the two components would have come into contact at a relative speed of about 3 meters per second in order to stick together in this way … This unusual shape could present a navigational challenge for the Philae lander team.
“The CNES release quotes Philae navigator Eric Jurado,” she continued, “as saying that ‘navigation around such a body should not be much more complex than around a nucleus of irregular spherical type, but landing the Philae probe [scheduled for November 11], however, could be more difficult, as this form restricts potential landing zones.’ ”
Only a handful of spacecraft have ever got up close to a comet (see the picture gallery of the others here). While a contact binary may be a surprise to scientists, the irregular shape spotted from afar was something that we’ve seen before in other comets.
“Irregular, elongated, and structured shapes are not uncommon for small bodies such as asteroids and comets,” stated the Max Planck Institute for Solar System Research in a release last week. “Of the five cometary nuclei that have been visited by spacecraft in close flybys so far, all are far from spherical.”
Makes us all eager to see what Rosetta finds out as it draws closer to the comet, for its rendezvous in August. The spacecraft will remain with the comet as 67P/Churyumov-Gerasimenko makes its closest approach to the Sun in 2015.
Some astronomers are already having fun imagining the possibilities of the new shape, such as the University of California, Berkeley’s Alex Parker.
This is really getting exciting! ESA’s Rosetta spacecraft (and the piggybacked Philae lander) are in the home stretch to arrive at Comet 67P/Churyumov-Gerasimenko in 34 days and the comet is showing up quite nicely in Rosetta’s narrow-angle camera. The animation above, assembled from 36 NAC images acquired last week, shows 67P/C-G rotating over a total elapsed time of 12.4 hours. No longer just an extra-bright pixel, it looks like a thing now!
The animation, although fascinating, only hints at the “true” shape of the comet’s nucleus. Reflected light does create a bloom effect in the imaging sensor, especially at such small resolutions, expanding the apparent size of the comet beyond its 4-by-4-pixel size. But rest assured that much, much better images are on the way as Rosetta gets closer and closer.
The spacecraft was about 86,000 km (53,440 miles) from 67P/C-G when the images were acquired. Since that time it has cut that distance in half, and by this weekend it will be less than 36,000 km (22,370 miles) from the comet. After more than a decade of traveling around the inner Solar System Rosetta is finally arriving at its goal! Click here to see where Rosetta is now.
Stay tuned for more exciting updates from Rosetta, and learn more about the mission below:
The illustration above shows the relative scale of the comet that ESA’s Rosetta and Philae spacecraft will explore “up-close and personal” later this year. And while it’s one thing to say that the nucleus of Comet 67P/Churyumov-Gerasimenko is about three by five kilometers in diameter, it’s quite another to see it in context with more familiar objects. Think about it — a comet as tall as Mt Fuji!
At the time of this writing Rosetta is 35 days out on approach to Comet 67P/C-G, at a distance of about 51,000 km (31,700 miles) and closing. Three “big burn” maneuvers have already been performed between May 7 and June 4 to adjust the spacecraft’s course toward the incoming comet, and after smaller ones on June 18 and July 2 there are a total of five more to go. See details of Rosetta’s burn maneuvers here.
Luckily the remaining burns are relatively small compared to the first three, with the final being very brief, so any data contamination by Rosetta’s own exhaust shouldn’t become an issue once the spacecraft has established orbit in August.
Launched in March 2004, ESA’s Rosetta mission will be the first to orbit and land a probe on a comet, observing its composition and behavior as it makes its close approach to the Sun in 2015. Click here to see where Rosetta is right now.
Note: While 3-5 km seems pretty big (especially when stood on end) comet nuclei can be much larger, 10 to 20 km in diameter up to the enormous 40+ km size of Hale-Bopp. As comets go, 67P/C-G is fairly average. (Except that, come August, it will be the only comet with an Earthly spacecraft in tow!)
Feeling thirsty? If you could somehow capture the water vapor from Rosetta’s comet, you would have the equivalent of two water glasses every second. That’s more than scientists expected given that Comet 67P/Churyumov–Gerasimenko is still screaming into the inner solar system at more than double the distance from Mars to the Sun.
“We always knew we would see water vapor outgassing from the comet, but we were surprised at how early we detected it,” stated Sam Gulkis, the instrument’s principal investigator at NASA’s Jet Propulsion Laboratory in California.
“At this rate, the comet would fill an Olympic-size swimming pool in about 100 days. But, as it gets closer to the Sun, the gas production rate will increase significantly. With Rosetta, we have an amazing vantage point to observe these changes up close and learn more about exactly why they happen.”
Comets are sometimes called “dirty snowballs” because they are collection of debris and ices. From their origin points in the outer solar system, occasionally one will be pushed towards the Sun.
As it gets closer, the ices bleed off and the comet develops an envelope of gases that eventually, with the Sun’s help, will turn into a tail. Some of the major “volatiles” include water, carbon monoxide, methanol and ammonia.
The observations were made on June 6 by an instrument called the Microwave Instrument for Rosetta Orbiter (MIRO), taken when the spacecraft was about 218,000 miles (350,000 km) away from its target. MIRO is trying to figure out the relative ratios of the ingredients of the coma, and will keep following along with the comet as it makes its closest approach to the sun in August 2015.
Rosetta, meanwhile, will get up close to Comet 67P/Churyumov–Gerasimenko by August and if all goes well, subsequently deploy a lander called Philae to check out the surface of the comet.