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Where Philae landed the second time
After years of investigative work, European scientists from the ESA mission Rosette now on comet 67P / Churyumov-Gerasimenko you can find the point where the landing module is located Philae had his second and penultimate ground contact on November 12, 2014. Left behind Philae Traces – and they reveal a lot about the comet.
 When Philae flew over the surface of Comet 67P, the lander hit the surface in several places. The excerpt shows the second touchdown site now identified.[Grafik mit dem gesamten Flug ber den Kometen] |
“Now we finally know the exact place where Philae touched the comet for the second time. This allows us to fully reconstruct the lander’s trajectory and derive concise scientific results from the telemetry data and measurements of certain measuring instruments that were switched on during the landing process, “explains Dr. Jean-Baptiste Vincent of the DLR Institute for Planetary Research, which is involved in the newly published research.
“Philae had given us a final riddle, “explains Laurence O’Rourke of the European space agency ESA, the rationale behind the search for” TD2 “, touchdown point 2, over the course of several years.” It was very important to identify the landing site, because that Philae Connected sensors indicated that the lander had made its way into the surface and most likely exposed the prehistoric ice below. “In recent years, the point has been shown in the numerous images and data from Philaes Landing area as sought after as the proverbial needle in a haystack.
Scientists continued to look at high-resolution images from the OSIRIS camera, a tool from the Max Planck Institute for Solar System Research (MPS) in Gttingen. Rosette-Orbiter, after patches of bare ice in the suspected region – unsuccessfully for a long time. Only the evaluation of the measurements with the ROMAP magnetometer, developed under the direction of the Technical University of Braunschweig fr Philae it was built to put scientists on the right track.
The team studied the changes in the data when the magnetometer boom, which protruded 48 centimeters from the lander, moved – that is, was bent – when it hit the surface. This resulted in a distinctive pattern in the ROMAP data that showed how the boom was relative to Philae moved. This allowed the researchers to estimate how long the probe had penetrated the ice. The ROMAP data was based on that of the RPC magnetometer Rosette related to the exact orientation of Philae to determine.
Data analysis proved this Philae he had spent nearly two full minutes – not unusual in this tiny gravity environment – at the second point of contact with the ground and had at least four different surface contacts as the probe “plowed” the rugged landscape. A particularly notable imprint that became visible in the images was made when the top of Philae it sank 10 inches into the ice on the side of an open crack, leaving visible traces of the tower and top. The spikes in the magnetic field data resulting from the arm movement indicated this Philae It took three seconds to create this particular “dent”.
ROMAP data helped uncover this point with the bright, ice-filled open fissure in the OSIRIS images. When viewed from above, the researchers reminded the researchers of a dead man’s head, and so they called the contact point the “crest of the skull.” The “right eye” of the skull arose when Philaes Top compressed the comet dust here while Philae like a windmill scraped through the gap between the dust-covered ice blocks to finally take off again and cover the last few meters to the final resting place.
“We saw it in the data at the time Philae he had contact with the ground several times and ended up in a poorly lit area. We also knew the approximate site of the final landing from the CONSERT radar measurements. The exact scenario of Philae However, the trajectory and exact points with ground contact could not be interpreted so quickly, “he recalls Philae-The project manager Dr. Stephan Ulamec of DLR.
Evaluation of the OSIRIS photos and the VIRTIS imaging spectrometer confirmed that the light-colored material is pure ice water produced by the Philae-The contact was exhibited on an area of 3.5 square meters. During this contact, the region was still in the shadows. It was only months later that sunlight fell on it, so that the ice still shone brightly in the sun and was barely weathered from the space environment and darkened, only other volatile ice like carbon monoxide or the carbon dioxide evaporated.
While this reconstruction of events alone is challenging investigative work, this first direct measurement of the comet’s ice consistency also offers important discoveries: ground contact parameters have shown that this billion-year-old ice dust mixture is extremely soft: it is more porous than the foam on a Cappuccino, the foam in the bathtub or in the foam crowns of the waves lapping the coast.
“The mechanical tension holding the comet ice together in this dust-covered chunk is only 12 Pascal. This is little more than ‘nothing’,” explains Vincent, who deals with the compressive and tensile strength of primitive ice. ” “which has been stored in comets for four and a half billion years as in a cosmic freezer as a testimony to the early hours of the solar system.
The survey also made it possible to estimate the porosity of the “rock” from which it was formed Philae has been touched: about 75 percent, or three quarters of the interior, is made up of cavities. The omnipresent “boulders” in the images are therefore more comparable to Styrofoam rocks in a fantastic landscape in the film studio than to real, hard, massive rocks. At another point, a six-meter-long block captured in several photos was even moving up the slope due to the pressure of the gas evaporating from the comet’s ice.
These observations confirm a result of the Rosette-Mission Orbiter, which determined a similar numerical value for the proportion of voids and showed that the interior of the 67P / Churyumov-Gerasimenko should be homogeneous up to a block size of one meter. This leads to the conclusion that the “boulders” on the surface represent the general condition of the comet’s interior when it formed about 4.5 billion years ago.
The result is not only scientifically relevant for the characterization of comets, which together with asteroids are the most primordial bodies in the solar system, but also allows estimates for future cometary missions, in which one of these “tail stars” is placed on one of these “tail stars” and you get sample material for its return to Earth should be what is currently being studied.
Philae it was gently removed from the mother probe in the afternoon of 12 November Rosette it separated and fell at the speed of a pedestrian in the direction of comet 67P / Churyumov-Gerasimenko. As images from the ROLIS DLR camera later showed, the approximately one cubic meter lander hit the planned Agilkia landing site almost perfectly. However, it could Philae do not anchor on the comet because the anchor harpoons intended for this did not ignite. Since the comet has only about one hundred thousandth of the earth’s gravitational pull on its surface, it crashed Philae from the comet, it rose to a height of one kilometer and hovered over the Hatmehit region on the smaller of the two cometary half-bodies.
After more than two hours I replied Philae: Even during the two hours Rosette The transmitted data showed that the probe had stopped following its turbulent flight, a sharp collision with the edge of the ground and two more ground contacts. A little later it might Philae also photos of the final landing site christened Abydos on Rosette ground radio. From these it quickly became apparent that the lander was now not as expected in a favorable position with sufficient sunlight.
For the DLR control room team, the work really only started after the unexpected landing: they operated the lander for almost 60 hours, commanded its ten instruments on board and, in the end, they turned it a little towards the rays. Of sun. However, the main battery power was running low because insufficient power could be produced. The batteries could not charge sufficiently because the sun only shone on the lander for just under an hour and a half for every 12.4 hours of comet.
Indeed, this has perplexed the hundreds Rosette– Team for 22 months, where Philae In fact it said: only a close-up of the OSIRIS camera, taken a few weeks before the end of the mission, on September 2, 2016, showed how
Philae it was stuck upright in a kind of crack under a ledge that shielded the sunlight. The space probe became the end of the mission Rosette on September 30, 2016, Churyumov-Gerasimenko also fell hard in a final maneuver.
The team reported on their analysis today in a specialist article in the journal Nature.
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