While sifting through images taken by the Rosetta spacecraft of Comet 67P, an amateur British astronomer has uncovered a previously unknown vertical cliff that looks like something right out of Mordor.
But it was Stuart Atkinson who noticed the one kilometer (0.62 mile) cliff. As he writes on his blog:
[As] soon as I saw that image I could see one area was just crying out to be cropped and turned into one of my landscape views – there was our best view yet of the towering cliff face on the inside of the small lobe…Looking at that part of the image I could see that with a little work (which turned out to be a LOT of work, but never mind!) those cliffs could be isolated and their true magnificence brought out. So, that’s what I started to do, and some time later this is what I came up with…
Looking at the foot of the cliff, you can see some relatively smooth terrain dotted by boulders, some of them as large as 20 meters (65 feet) across.
It may look daunting, but owing to the extreme low gravity on the comet, a human could actually survive the jump.
I am so, so happy about that, seriously. Not just because personally it is nice to have an image which took a long time to make being seen and shared so widely now, but mainly because it shows why the ESA decision to regularly release navcam images from the ROSETTA mission was the right one to take – it has allowed people like me to use ROSETTA images for Outreach, and to promote the mission to the media and the public. Every reTweet and every FB share and comment proves how much interest in the mission there is out here. People are blown away by that image and the view of the cliffs it shows, so thank you AGAIN to ESA for letting us see the navcam images and allowing us to use and play with them!
Image credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0/Stuart Atkinson
As Comet 67P/Churyumov–Gerasimenko sneaks closer to the sun, the Rosetta orbiter is capturing dramatic outbursts from the ever-more active comet. This jet was so powerful, it momentarily out-puffed the solar wind, creating a rarely-observed diamagnetic cavity.
The quiescent comet on August 6, 2014 and the far more active comet year later on August 6, 2015. Image credit: ESA/Rosetta/NavCam
This beautiful jet appeared, spurted gas and jet into space, and vanished again all in under an hour on July 29, 2015. The jet originated from the rugged Anuket region on the comet’s neck. The Rosetta spacecraft was 186 kilometers above the comet’s center of mass at the time of the outburst.
The outburst produced a diamagnetic cavity, a temporary drop in the comet’s magnetic field. The comet is not magnetic, so its magnetic field is entirely the result of the solar wind. With gas escaping from the comet at a velocity of at least 10 m/s, researchers suspect the jet’s outburst was powerful enough to deflect the solar wind. The outburst of gas temporarily shoved the perpetually-smothering solar wind farther from the comet’s nucleus than usual, changing the pressure balance. It was powerful enough to push this cavity all the way out to Rosetta, creating a magnetic field-free region that stretched at least 186 kilometers away from the comet.
“Finding a magnetic field-free region anyway in the Solar System is really hard, but here we’ve had it served to us on a silver platter – this is a really exciting result for us.”
The science team was hoping to find diamagnetic cavities on Comet 67P/Churyumov–Gerasimenko, although smaller than the one observed on Comet Halley. The new observations of this brief pocket in the solar wind will provide important data on comet/solar wind interactions.
The July 29 jet coincided with a temporary drop in the comet’s magnetic field strength, producing a diamagnetic cavity. Image credit: ESA/Rosetta/RPC/IGEP/IC
“This first ‘quick look’ at our measurements after the outburst is fascinating. We also see hints of heavy organic material after the outburst that might be related to the ejected dust. But while it is tempting to think that we are detecting material that may have been freed from beneath the comet’s surface, it is too early to say for certain that this is the case.”
The gas envelope surrounding the comet, or its coma, had twice the carbon dioxide (CO2), four times the methane (CH4), and seven times the hydrogen sulphide (H2S) after the outburst compared to two days earlier. The nasty-smelling combination has draped the comet in the stench of rotting eggs and farts, offering faint mercies that the highly-anthropomorphized Rosetta spacecraft isn’t actually alive and possessing a keen sense of smell to go with the mass spectrometer. Of all the gases monitored by the instrument, only the water (H2O) content stayed roughly constant.
The dust also stepped up its game, increasing by a factor of ten after the outburst. The dust counter typically picked up 1 to 3 hits per day in early July, which increased to 30 hits per day 14 hours after the outburst, and briefly peaking at 70 hits within a 4-hour window the following day. The GAIDA dust counter’s principle investigator Alessandra Rotundi points out it wasn’t just the sheer amount of dust that increased, but also its velocity:
“It was not only the abundance of the particles, but also their speeds measured by GIADA that told us something ‘different’ was happening: the average particle speed increased from 8 m/s to about 20 m/s, with peaks at 30 m/s – it was quite a dust party!”
Comet 67P/Churyumov–Gerasimenko will reach perihelion, its closest approach to the sun, on Thursday August 13, 2015. Image credit: ESA
The comet is most active at perihelion because sunlight is flooding into areas that have been shadowed for years, suddenly bumping surface temperatures. The comet’s activity is expected to lag, peaking in the weeks following perihelion on Thursday. While in this highly active phase, the Rosetta spacecraft is pulling up to 300 kilometers away from the surface to hopefully avoid the worst of the shedding boulders, jets, and any other unpredictable activity.
Key stages in the mission include Rosetta’s maneuvers as it prepared to dispatch Philae to the comet’s surface, close flybys in February and March of 2015, and course corrections performed to protect the probe from the comet’s increased activity in August 2015. In the spring of 2016, Rosetta went on another far excursion, followed by a close flyby when its instruments made several critical observations.
Starting in August 2016, the probe began to fly a series of elliptical orbits that brought it progressively closer to the comet. On September 29th, Rosetta was deliberately maneuvered onto a collision course with the giant rock. The probe struck the surface on September 30th in the Ma’at region on the comet’s head, finally ending the historic mission.
Watching the simulation, it’s important to point out that, while Rosetta’s trajectory is accurate, the comet’s rotation is not. The arrow indicates the direction to the sun as the camera viewpoint changes over the course of the simulation.
Japan’s Proximate Object Close Flyby with Optical Navigation (PROCYON) has been lost in space ever since its ion thrusters blew out in 2014. Since then, the tiny spacecraft has done its best to be useful, orbiting the Sun by itself. A new study reveals the PROCYON made some impressive observations on Comet 67P/Churyumov-Gerasimenko, the same comet the Rosetta spacecraftobserved for two years before ending its mission in 2016.
In September 2015, an international team of researchers used PROCYON’s LAICA telescope to observe Comet 67P while Rosetta was still inside the cloud surrounding the nucleus of the comet, called the coma. The micro spacecraft happened to be in the right place at the right time—though the researchers weren’t planning to use PROCYON to observe Comet 67P, at the time, it had a better view of the comet than Rosetta. For this reason, it was able to accurately measure the amount of water discharge on the comet. The researchers’ findings have been published in the February 2017 edition of The Astronomical Journal.
“The water production rate of a comet is one of the fundamental parameters necessary to understand cometary activity when a comet approaches the Sun …because water is the most abundant icy material in the cometary nucleus,” researchers wrote.
By studying the quality and quantity of water on comets, we might better understand the origins of water on Earth. It’s long been hypothesized that a barrage of meteorites crashing into Earth could be responsible for some of the water on our Blue Marble. More generally, studying the activity on the surface of comets can shed light on how these mysterious balls of ice and rock have evolved over the history of the solar system.
The team was able to take its measurements and use them test out water production rates on a coma model, which allowed them to confirm an intriguing relationship: the closer an object is to the Sun, the higher its water production rate.
It’s a big achievement for a wayward spacecraft. According to the research team, these measurements mark the “first scientific achievement by a micro spacecraft for deep space exploration.” Because micro spacecrafts are remarkably cheaper than their larger siblings, the team hopes this feat will be a “model case” to inspire more micro spacecraft missions.