Nasa's Mercury spacecraft ends four year mission by crashing into tiny planet
The only spacecraft ever to orbit Mercury ended its four-year tour with a crash landing on Thursday. Nasa's Messenger plunged from orbit as planned and slammed into the sun's closest planet at about 14,081km/h, creating a crater an estimated 16 metres across. Messenger became the first spacecraft to orbit hot, little Mercury, in 2011. It circled the solar system's innermost planet 4,105 times and collected more than 277,000 images.
"Today we bid a fond farewell to one of the most resilient and accomplished spacecraft ever to have explored our neighbouring planets," lead scientist Sean Solomon, director of Columbia University's Lamont-Doherty Earth Observatory said.
Solomon noted in a statement that Messenger set a record for planetary fly-bys - once past Earth, twice past Venus and three times past Mercury before entering Mercury's orbit - and survived "both punishing heat and extreme doses of radiation" to surpass expectations. Flight controllers managed to keep the spacecraft going a few extra weeks by using helium gas not originally intended as fuel. But the tank finally emptied and gravity's relentless tug ended Messenger's illustrious voyage. Mercury is the last of the rocky inner planets in our solar system - also counting Mars and Venus - to be studied up close by mankind.
Thursday's crash occurred on the side of Mercury facing away from Earth and its telescopes. Several minutes passed before Nasa received confirmation of the crash landing. Controllers received no signal from Messenger when it was supposed to be back in the coverage zone - a sign that the spacecraft, measuring over three metres wingtip to wingtip, had, indeed, succumbed to gravity.
"Well I guess it is time to say goodbye," the Messenger Twitter feed stated as the end drew near. Then after the impact: "On behalf of Messenger, thank you all for your support. We will continue to update you on our great discoveries. We will miss it."
Astronomers who used Messenger to detect Mercury's frozen water-covered poles and significantly off-centre magnetic field called it the end of an era. Other discoveries: volcanic deposits that are evidence of the planet's eruptive past, and noticeable global shrinkage.