UPDATE: August 6, 2014. ARRIVAL SUCCESSFUL. The final CAT burn was flawless and Rosetta is now traveling in tandem with its comet, currently starting the first pyramid (really tetrahedron) orbit.
Images above show the nucleus of Comet 67P/Churyumov–Gerasimenko, which is smaller than many mountains, is also much smaller than both of the Mars moons, Phobos and Deimos.
Looks like that ‘smoother’ area has some ice boulders and / or icy outcrops.
Many features look like ablation features, even though comet 67P/Churyumov-Gerasimenko has only been in an orbit to allow sublimation only very recently, so could be impact features that have frozen.
Follow the links below for more on this exciting space mission:
As you can see from the image above, the NavCam is an incredible camera in its own right. The nucleus of Comet 67P/Churyumov–Gerasimenko is 3.5 by 4 kilometers – smaller than many mountains, is also much smaller than both of the Mars moons, Phobos and Deimos. And yet from 300 kilometers / 186 miles away, the shape of the nucleus is clearly visible and a wealth of surface details are showing.
There will be another Close Approach Trajectory burns (CAT burns) on Wednesday, August 6, 2014, slowing the spacecraft by another 1 meter per second. Then the Rosetta Spacecraft will be only 100 kilometers / 62 miles from the comet, traveling in tandem with the comet.
The 3.5-by-4-km-sized nucleus of Comet 67P/Churyumov–Gerasimenko has now been seen closer in at a distance of 1,950 kilometers / 1,212 miles by the Rosetta Mission OSIRIS NAC camera. Surface features on the nucleus are now becoming very apparent in this 37-meter resolution image.
The linear depressions and hills now appear to be layers on the larger lobe. Both lobes are showing very hilly terrain.
The ‘neck’ linking both lobes appears very reflective and also quite smooth, perhaps a shorter version of the smooth ‘neck’ seen on Comet 103P/ Hartley by the NASA Deep Impact spacecraft. Looks like possible fresher ice, but upcoming closer views will be needed to ascertain the nature of the brighter material.
This is astonishing stuff. Although the image still looks a tiny bit pixelated, this is actually high resolution, showing how small the nucleus of Comet 67P/Churyumov–Gerasimenko really is. However the resolution will increase enormously each day now.
Closer images of Comet 67P/Churyumov–Gerasimenko are in now, as the Rosetta spacecraft approaches. These three images [above] are separated by two hours. The rotation of the nucleus of Comet 67P/Churyumov–Gerasimenko, is reasonably slow, completing a rotation on it’s axis approximately every 12 hours, 36 minutes.
The image shows the 3.5-by-4-km-sized nucleus of the comet seen closer in at a distance of 5,500 kilometers / 3,400 miles by the Rosetta Mission OSIRIS NAC camera. Surface features on the nucleus are now becoming apparent in these 100-meter resolution images. Looks like the impact crater I suspected on the bulbous lobe does exist, and there appear to be some linear depressions and hills on the larger lobe. Both lobes are beginning to show hilly terrain.
The neck linking both lobes of the comet appears very reflective. Looks like possible fresher ice, but upcoming closer views will be needed to ascertain the nature of the brighter material.
The final Far Approach Trajectory Burn (FAT Burn) – on Wednesday, July 23 – successfully reduced the speed of the spacecraft with relation to the comet by a further 5 meters per second or 18 kilometer per hour / 11 miles per hour.
UPDATE July 22, 2014. We see the comet as a contact binary: There have been fascinating developments regarding the Rosetta spacecraft mission to Comet 67P/Churyumov–Gerasimenko, during the final days of approach. The comet is turning out to be a contact binary, or it is a weird ablated eroded object. The double nature of the nucleus is about to be unravelled as Rosetta becomes the first space mission in history to rendezvous with a comet, escort it as it orbits the sun, and deploy a lander.
What do these new images represent? Are they bits off the same parent body or indeed two entirely separate comets that made a light contact and fused or froze together?
Or is this shape due to a formerly more spherical object that over time has ablated to the strange shape?
What is next for Rosetta’s exploration of Comet 67P/Churyumov–Gerasimenko? Some highlights of the mission below.
The next image release is July 24, 2014 after the final Far Approach Trajectory Burn (FAT Burn), which will reduce the speed of the spacecraft with relation to the comet by a further 5 meters per second or 18 kph / 11 mph. These new images will be from much closer in.
August 3, 2014 and August 6, 2014. There will be Close Approach Trajectory burns (CAT burns) on these two dates, slowing the spacecraft a further 3 meters and 1 meter per second respectively. Then the Rosetta Spacecraft will be only 100 kilometers / 62 miles from the comet traveling in tandem.
Throughout August and September, 2014. A further short burn is planned post-arrival, which will reduce the distance further to 70 kilometers / 43.5 miles. Rosetta will then do a do-si-do with the comet, forming a so-called Pyramid Orbit (though it will really be a Tetrahedron Orbit rather than a pyramid). At this point, the spacecraft will be imaging the comet’s nucleus from different angles and solar illuminations.
October, 2014. Rosetta will move closer still, perhaps to less than 5 kilometers / 3 miles from the comet this time to complete a search for the landing site.
November 11, 2014. The piggybacking Philae lander is due to separate from the Rosetta spacecraft and land on the comet on this date. The date may change slightly, perhaps a week or so later if a safe landing site proves difficult to find.
Immediately after touchdown, Philae will fire a harpoon into the surface to anchor to the comet. The surface gravity is extremely weak on the comet and Philae could easily bounce back up into space. Then almost immediately Philae will start operations as time will be of the essence, due to the unpredictable nature of this comet.
Philae is expected to operate for seven days, possibly longer, providing panoramas of the surface, close up views of the surface, sampling material drilled from the surface and measuring the composition of any gas. One thing will be to measure the ration of Heavy Water – aka Deuterium enriched water – with respect to regular water and compare with Earth’s oceans. Heavy Water accounts for one part in 6,420 in the Earth’s oceans.
One objective for Philae is to determine if the comet’s ice has a similar ratio of heavy water, did former Kuiper Belt comets in the early solar system bring none, some, much or all of Earth’s water. So far research with other comets from Earth-based spectrometers as well as by flyby spacecraft appear to show that this is not so.
However one comet, 103P/Hartley turned out to be a perfect match. More recently comet C/2012 S1 ISON which disintegrated last November just prior to a sungrazing perihelion was also a perfect match. However comet C/2012 S1 ISON was not a Kuiper Belt comet, but was fresh from a one off seven-million-year journey from the postulated Oort Cloud, some one light year from the sun. So the mystery deepens.
Another priority is to check for basic prebiotic organic chemistry. Does Comet 67P/Churyumov–Gerasimenko carry the ingredients for life? Did comets in the early solar system not only bring water, but did they also bring the ingredients for life to the young Earth, possibly to Mars too?
After Philae stops operating, the Rosetta Spacecraft will continue constant monitoring of the comet as it continues to move closer to the sun, warming the surface, increasing activity from jets, enlargement of the coma – a huge shell of gas surrounding the nucleus – and monitoring the growth of the tail.
August 13, 2015. Comet 67P/Churyumov–Gerasimenko reaches perihelion, its closest point to the Sun on this date, when the distance from the sun will have reduced to 1.29 AU (1.29 times the Sun to Earth distance), 193.5 million kilometers / 120.2 million miles. Solar heating will be at its greatest.
There may be a lag effect with the comet not reaching its highest temperatures until after perihelion, in much the same way that the warmest time of the day is in the afternoons not midday, or the warmest month in many parts of the Northern Hemisphere is usually August, not June. Navigation of the Rosetta spacecraft will be crucial as ice particles, dust and so on could well be ejected from the comet at high speeds, and there is a chance the Rosetta Spacecraft could be destroyed or at least fatally damaged, with ice particles and dust impacting the huge solar arrays for instance. The mission’s primary objectives are expected to be completed well before perihelion.
However, if Rosetta survives perihelion, then a unique opportunity to monitor a comet during its initial quietening down phase will present itself.
At that point, however, onboard fuel supplies will be dwindling, and solar arrays may have suffered some damage and be degrading.
Space engineers may attempt to land the Rosetta spacecraft on the comet, perhaps in September or October 2015, in a different location to Philae, obtaining images and other data during the descent. Unlike Philae, Rosetta was not designed to land, but could survive a very soft landing for a short period.
Also to mention for scale, this comet would easily fit inside Mt Everest, K2, etc with plenty of room to spare.
Bottom line: Updates and what to expect from Rosetta spacecraft as it approaches Comet 67P/Churyumov–Gerasimenko.
Andrew R. Brown lives in Ashford, Kent, United Kingdom and works for local government, Kent County Council. He is directly involved with sharing ideas and thoughts with several NASA missions, particularly the Mercury MESSENGER mission, and has struck up good relationships with the MESSENGER team and the Mars Science Laboratory Curiosity rover team. He has suggested quite a few observations that were then carried out by the Mars Reconnaissance Orbiter HiRISE instrument. Earlier, some of his suggested observations of Jupiter's moon Io were carried out by the New Horizons spacecraft, now on its way to a Pluto encounter in 2015.