Landing on a comet is a fact
Kamal Lodaya, The Institute of Mathematical Sciences, Chennai

The first attempt
On 12th November 2005, 29 crore kilometres from Earth, the Japanese spacecraft {Hayabusa} (the name means "falcon") sent a small half-kilogram lander {Minerva} (a Greek goddess symbolized by her owl) down on a small asteroid called Itokawa.
The spacecraft had been launched in 2003 and had taken two years to travel from Earth to this asteroid. Itokawa looks like a dirty groundnut about half a kilometer long. It is named after a Japanese rocket scientist. Most asteroids orbit the Sun between Mars and Jupiter. At its nearest approach to the Sun ({perihelion}) Itokawa is between the Earth and Mars, at its farthest ({aphelion}) it is a little outside the orbit of Mars.
Minerva missed Itokawa's tiny gravitational pull, fell into space and was lost. Hayabusa successfully returned to Earth in 2010.

The second attempt
Soon after the Japanese, the European space agency launched the {Rosetta} spacecraft in 2004. The name is after a place in Egypt, the town is called Rashid in Egyptian. Rosetta headed for a comet, named Churyumov-Gerasimenko after its discoverers. The comet is closest to the Sun (at {perihelion}, next in August 2015) a little outside the orbit of the Earth. At its farthest from the Sun it reaches the orbit of Jupiter. 
On 12th November this year, 51 crore kilometres from Earth, Rosetta sent a 100-kilogram lander {Philae} down onto the comet. The name stands for an Egyptian temple to a goddess. After a 7-hour journey, Philae hit the comet, but it bounced! Two harpoons were to be fired into the comet to prevent this, but they did not fire.
From the signals sent by Philae to Rosetta and relayed by Rosetta to Earth, we know that it bounced around one kilometre (this is the all-space record for long jumps) and then again bounced, before stopping on the surface of the comet. An instrument on Philae detected that it sank 10 or 20 centimetres through a dusty or fluffy surface before it hit something hard which made it bounce.

Success
Philae sent back several pictures. We show you one of these, which was processed by video analyst Mattias Malmer by adding a depth perspective, as our eyes do when we see landscapes on Earth. You can see one of Philae's landing wheels hanging on the left, above the comet's surface. Other landing wheels are on the comet. This is a real photograph, only the depth information is added. The comet has no atmosphere. Its landscape looks jagged and rocky. Philae has not been found on the comet, but it is suspected that the landing site is on the edge of a crater.
Philae has batteries which last about 60 hours. Unfortunately the bounce put it in the shade of a rock on the "winter" side of the comet which gets little sunlight so the batteries could not be recharged. Even then Philae carried out a series of science experiments before its batteries ran out.

Science on a comet
The first experiment failed to find dust moving near the lander, so the landing site is not spewing out dust as the "active" parts of a comet do. The temperature is very cold, around 170 degrees Celsius {below zero}. Another experiment sent electric current (AC) from one electrode to another through the comet surface below the lander. This suggests that there is a lot of water ice under Philae. A third experiment hammered sideways into the comet's surface, but this failed, which suggests that most likely next to Philae is a wall of very cold and hardened ice.
A fourth experiment operated a drill, which worked, but the drill does not seem to have picked up any material for a lab on Philae to analyse. It is possible that instead of drilling into the comet, the comet wall pushed the whole lander back. Again this suggests that the wall is very hard. 
This experiment also tried "smelling" the area above the surface, and this has succeeded, finding complex componds made of carbon. We do not yet know exactly what these compounds are. Many people are excited that these compounds might be related to life, but it is likely that the compounds are other carbon-filled substances. By the time this {Jantar Mantar} is in your hands the analysis should be done and the answer known.
ESA scientists are hoping that next year when it becomes "summer" at the Philae landing site, the sunlight will recharge its batteries and it might again start working and doing experiments. If it happens this will be a historic event.