Riding piggyback on a comet – the aftermath

At about 7 AM (IST) on 15^th November 2014, European Space Agency's comet lander Philae, sent the last round of data to earth and went into hibernation, because of low batteries. Ever since then, people around the world have been curious to know, whether Philae did succeed in sending some new information about the materials- the comet is composed off?

Well! Luck seems to be on our side, though partially! In spite of it's very short active life of only 57 hours on 67P comet, it seems that Philae has managed to spend some crucial information back to earth that should add to our knowledge of comets.

The most important observation made so far relates to what Philae has found out about the atmosphere over the comet. According to the DLR German Aerospace Center, the Cometary Sampling and Composition (COSAC) gas analysing instrument on Philae was able to 'sniff' the atmosphere above the comet and has detected after landing, organic molecules containing carbon elements. Organic molecules form the basis of life on Earth. This observation by Philae is important from point of view of many scientists, who believe that life evolved on our planet only after organic molecules were passed on to earth by comets that impacted with earth.

Philae has also successfully carried out another experiment before it's hibernation, in which a penetrator was hammered in comet's surface and related temperature rise in the penetrator was measured with sensors. This penetrator was equipped with multi purpose Sensors for Surface and Subsurface Science (MUPUS) tool to measure the density and thermal and mechanical properties of the comet's surface.

The penetrator was expected to go to depth of 40 Cm after hammering. However, it did not go that far deep in spite of the hammer setting being cranked up to its highest level. According to DLR, after passing through a 10-20 cm thick layer of dust, the sensor hit a layer of material estimated to be as hard as ice. Scientists were expecting the comet's surface to be much softer. Tilman Spohn, who leads the MUPUS team at the DLR, says in a statement issued on 18^th November 2014; "It's a surprise. We didn't expect such hard ice on the ground.”

It was also reported that during dying hours of the battery, Philae had drilled into the comet's surface in its hunt for organic molecules. However so far no word has come, whether any sample of drilled materials was submitted to COSAC for analysis.

The two observations made by Philae; finding of hard ice on the surface and presence of organic molecules in the atmosphere; appear to be of great significance to us and could lead to better understanding of comets in future.

Comet 67P would be going nearer and nearer to the sun for next 6 months. There is a possibility that Philae's solar batteries might get charged again if sunlight falls on the solar panels. In that case Philae can come back to life and could complete the tasks left unfinished.

20^th November 2014

Riding piggyback on a comet – Day 2

(continued from Day 1)

As the day progressed, the euphoria caused by this fantastic achievement started to wane bit by bit, as bad news kept trickling. I had mentioned in the previous article, that two harpoons, that were supposed to be fired to anchor Philae on ground because 67P comet is a small mass moving in space with extremely low gravity ( 1/100,000th that of Earth), did not get fired at all. In fact this washing machine sized probe weighs just unbelievable 1 gram on comet because of its low gravity. The harpoons were supposed to hold the probe against the surface of the comet and since they did not fire, Philae is sitting their just because of the gravitational force of its weight of 1 gram. Scientists recognize this as highly unstable and dangerous situation.

News for more trouble started coming in. Because the two harpoons failed to get fired, Philae just could not be anchored to the surface of comet at first touch down at 15.33 Hrs and bounced off the surface of the comet like a tennis ball and drifted through the void for almost two hours before touching down again at 17:33 Hrs. According to some reports, this bounce could have been as high as a mile or 1,6 Km. Even at this time it did not settle down on surface and bounced off again, though with a smaller bounce. After another 7 minutes it finally settled on the surface at 17:41 Hrs. in a shallow crater on the comet's 2 mile wide body.

With the stability problem being solved temporarily, a new problem cropped up. Philae has a primary battery and secondary solar powered batteries. Scientists detected that they were hardly getting any solar power at all as during the 12 hour day, the comet received illumination for just 1.5 hours. The reason for this problem was found out to be the place where Philae was resting after the second bounce. It was sitting next to a cliff that was about few meters away and it was in the shadow of the cliff permanently. This meant that the shadow was blocking the sunlight from reaching to solar points.

This has brought about a new dilemma for the mission control scientists. With the primary battery slowly running out, they need to decide the use for which this power is to be used. There are 4 scientific instruments that can reveal tomography of the comet and data showing whether the matter it is made of is magnetized? The primary battery can run these experiments for a few days without the help of solar batteries. On the other hand, some acrobatic maneuvers can be tried to get the solar panels out of the shadows so they can keep Philae going for a few more months. However if this fails, the mission control will neither receive any data from the experiment nor would be able to move the craft out of shadow. This would mean that Philae's useful lifetime may now be much shorter and it would just keep sitting on surfaced of the planet in a mode of hibernation for the coming months. The comet is on a 6 ¼ year elliptical orbit around the sun, and at the moment it is getting closer to the sun. There is a chance that Philae might wake up again if its solar panels catch more light. But that is just a chance.

It appears that mision control scientists have decided to collect as much data as possible while its primary battery still has energy before trying any risky maneuvers. Philae's scientific instruments have already begun gathering reams of data to send back to Earth, including the first pictures taken from the surface of a comet. The first photos reveal the comet's rocky terrain, include one that showed one of the lander's three feet in the corner of the frame.

Another experiment was carried out in which a penetrator was hammered in comet's surface and related temperature rise was measured with sensors. This could give important clues regarding composition of the ground.

Because Philae is sitting their just with its own weight of 1 gram, scientists are figuring out whether an important planned experiment can be tried out This experiment involves drilling into the comet to extract some of the material buried beneath the surface. But drilling without the craft not being properly anchored can be dangerous as it can tilt or even lift off the lander. This experiment is important because scientists want to analyze the material of the comet as it has remained almost unchanged for 4.5 billion years, making it something of a cosmic time capsule. However as per latest news, mission control has decided to go ahead with drilling as the batteries may not last beyond Friday ( 14-November 2014).

Around 7PM (IST) on 14^th November 2014, Philae started drilling on the surface of the comet. Around midnight, another attempt was made to rotate Philae to see whether it could get more sunlight to charge its batteries. Finally around 7 AM (IST) on 15^th November, Philae sent the last round of data including analysis of the drilling samples, before its batteries went dead and it went into hibernation. It would revive only when sunlight falls on the solar chargers. Whether the data sent by Philae reveals at least some new information about the materials, the comet is composd off, we should know in a day or 2.

After Philae has gone dead, scientists can still receive data from the mother ship Rosetta, which carries on board 11 instruments to analyze the comet, over the coming months. Let us wait and watch.

15^th November 2014

Riding piggyback on a comet- Day 1

The tweet came exactly at 9.30 PM (Indian standard time) from an unknown twitter handle and said Philae Lander @Philae2014 Touchdown! My new address: 67P! #CometLanding. With this, began a new experience and a relationship for the entire mankind, never before attempted in history.

Philae is the name of a robotic probe lunnched by European Space Agency aboard its mother space- craft Rosetta. The pair blasted off into space in 2004, and took more than a decade to reach its target; 67P/Churyumov-Gerasimenko Comet in August 2014. Similar to India's Mars orbiter, Rosetta too used the gravitational pull of Earth and Mars as slingshots to build up the speed.

Rosetta-Philae pair had to travel more than 510 million kilometres (320 million miles) from Earth to reach the comet. The mission was approved in 1993 and has costed about 1.3 Billion Euro to ESA. The first major obstacle faced by Rosetta was its passage very close to an asteroid 250 million miles from Earth. The spacecraft was made to loose its radio signal for 90 minutes during this flyby of the Steins asteroid, also known as Asteroid 2867. Waking up after almost three years of hibernation, Rosetta sent its first signal back to Earth on January 20^th, 2014. Systems had been powered down in 2011 to conserve energy, leaving the scientists in the dark for 31 months. The pair finally separated from each other, some 9 hours earlier to touchdown (approximately around noon IST) on Wedensday, 12^th November 2014. This was confirmed by the ESA Rosetta Mission @ESA_Rosetta, in a tweet at about 3 PM (IST) on Wednesday November 12^th, 2014 as “ SEPARATION CONFIRMED! Safe journey @Philae2014!”

The European Space Agency correctly considers this first-ever landing on a comet, a crowning phase in the quest to explore the origins of the Solar System, but many of the readers must have felt puzzled as to why landing a probe on a comet like 67P, that is travelling towards the Sun at 18 kilometers per second (11 miles per second), when there are planets like Mars that are yet to be investigated fully.

The Comet known to astronomists as 67P, is officially designated 67P/Churyumov–Gerasimenko. It was discovered in 1969 by Klim Ivanovych Churyumov of the Kiev National University's Astronomical Observatory. It is a comet with a current orbital period of 6.45 years around the sun and a rotation period of approximately 12.4 hours and travels at a break-necking speed of 135,000 km (84,000 mi) per hour. It is expected to come to its perihelion (closest approach to the Sun) on 13 August 2015. Readers would be able to realise that with such a short orbital period, Philae lander, riding piggy back on 67P, (if it can be made to stay there safe and sound) is going to have a tour of the entire solar system in just 6 years.

A comet is an icy small Solar System body that, when passing close to the Sun, heats up and begins to outgas, displaying a visible atmosphere or coma, and sometimes also a tail. With 67P approaching the sun next year in Agust 2015, Philae would have a great opportunity to examine the coma and the tail. Many comets have collided into Earth in its early stages. Many scientists believe that comets bombarding the young Earth about 4 billion years ago brought the vast quantities of water that now fill the Earth's oceans, or at least a significant portion of it. The detection of organic molecules in significant quantities in comets has led some to speculate that comets or meteorites may have brought the precursors of life—or even life itself—to Earth.

However, we humans have always regarded Comet sightings as bad omens that would bring major disasters such as wars, floods or even black plagues. The best-known example is probably Halley's Comet of 1066, which was considered as a "bad omen" for King Harold II of England but a "good omen" for William the Conqueror. However these beliefs are now all gone and people look at comets for finding solutions to unsolved questions like origin of life.

The landing of Philae on comet 67P could have been considered as a great unqualified success, but unfortunately not everything seems to have gone correct. Because 67P is a small mass moving in space, ESA scientists had planned to fire immediately after touchdown, 4 harpoons to anchor the lander to the ground and prevent it escaping from the comet’s extremely weak gravity. The harpoons were expected to support Philae during extreme turbulence conditions. Initially, mission control had confirmed that Harpoons were confirmed as fired & reeled in. However mission control confirmed later that something has gone wrong when they tweeted: Hang on in there Philae! MT @Philae2014: I’m on the surface but my harpoons did not fire. My team now trying to determine why. The surface of the comet also appears to be soft, which is possibly why Philae has not been able to secure itself.

Whatever is the final outcome, we shall know in a few days. Meanwhile Philae has started taking photographs, which would certainly show the environment on the comet itself. This space mission is an incredible achievement and requires to be seen in that light. We all should congratulate ESA scientists for this great feat.

( Continue to read report for Day 2)

13^th November 2014