Sen—In just a few days time, another of our planetary probes will end its mission in dramatic style when it crashes to destruction.
NASA’s MESSENGER spacecraft will be the first to hit Mercury, the innermost world in the Solar System, on or about April 30 after its fuel finally runs out. The impact will mark the end of a remarkably successful mission, as described by my fellow Sen blogger Emily Ladkawalla this week.
MESSENGER’s demise comes just a few weeks after the loss of a previous long-serving envoy to an inner world, the European Space Agency’s Venus Express. This probe, a cut-price mission based on Mars Express and built with spare parts from both that mission and Rosetta, stopped working in December, 2014, when its fuel was exhausted.
Its final manouevres had included dips to taste Venus’s poisonous atmosphere, and that dense atmosphere will have destroyed it completely in its final death dive some time in January.
I have previously written about the number of probes that have been crashed into the Moon, often for operational and research reasons. For probes orbiting the outer planets, they can be given a similar fate for motives that can be best summed up as environmental protection.
Take NASA’s Galileo probe for example. Launched from the Space Shuttle Atlantis in 1989, Galileo reached Jupiter in 1994 before orbiting our largest planet for nine years, studying it and its retinue of moons as never before.
But the nature of those discoveries led mission controllers to conclude that they could not safely leave Galileo loose in its orbit at the end of its working life. Studies of three of Jupiter’s largest moons, the Galilean satellites, Europa, Ganymede and Callisto, revealed that they probably had subsurface oceans of liquid salt water.
There was a chance therefore, however slim, that Galileo might one day collide with one of those moons and contaminate it with any microbes it had carried from Earth. NASA decided such a risk could not be taken, and so the probe was deliberately sent plunging into Jupiter’s own dense clouds in September 2003.
Recently another hugely successful NASA mission has been informing us about the neighbourhood of the second of the Solar System’s gas giants, Saturn. Cassini went into orbit around the planet with the spectacular ring system in July 2004.
More than a decade later, it is still carrying out fantastic science, but again the planet’s moons, which might conceivably be home to some kind of life, must be protected from contamination in the event of a crash. Cassini will therefore be sent to be crushed by Saturn’s own dense atmosphere in 2017, taking the chance to send back some information about its cloud tops as it goes.
Of course, there is another planet in the Solar System that has seen numerous spacecraft come to a fiery end—our own Earth. Decaying satellites, rocket stages, and other debris routinely re-enter the atmosphere to be destroyed in a blazing fireball.
There has even been an interplanetary probe sent to its fate in our atmosphere. Japan’s Hayabusa probe, having made a seven-year trip through the Solar System to accompany the asteroid Itokawa, burned up after firing a capsule containing fragments of it into the Australian Outback in June 2010.
Recently it has been a way to dispose of Europe’s five Automated Transfer Vehicles (ATV) which successfully delivered cargoes to the International Space Station between 2008 and 2014. The last one, the Georges Lemaître, burned up in February.
Current plans are for the International Space Station itself to go out in a similar fashion, some time after 2024. This orbiting collossus is too big to be destroyed completely during a re-entry, so is expected to be sent on a deliberate course into an uninhabited region of the Pacific Ocean.
Russia already has experience of deorbiting space outposts, having ended the working lives of its Salyut and Mir space stations in this way. NASA’s own early space station, Skylab, enjoyed a less controlled re-entry that sent chunks crashing onto Australia in July 1979.
Thankfully, they came down in a relatively sparsely populated part of the continent, near Balladonia, Western Australia, but the incident had amusing consequences. Some fragments had fallen on the small town of Esperance, 580 km (360 miles) east of Perth. Somewhat put out, the local authorities decided to fine NASA for dropping litter and sent the space agency a bill for the equivalent of USD $400. But NASA ignored it, (showing less regard for the habitat of wild kangaroos than the environment around distant moons, perhaps), and local councillors shrugged their shoulders and decided to write the “fine” off.
One local lad did make some cash from the crash, however. The San Francisco Examiner offered a prize of $10,000 for the first piece of Skylab to be delivered to their offices. Stan Thornton, then 17, collected fragments from the roof of his home in Esperance and caught the first flight to San Francisco where he picked up his prize.
The story does not end there. In 2009, billboards were erected around Esperance to remind people of NASA’s unpaid debt. Radio host Scott Barley, of California’s Highway Radio, heard about this and appealed for funds on his morning show. He came up with the required sum, which he then delivered in person.
Esperance has also benefited from the re-entry, with its place in space history making it a big draw for tourists. There is a scale model of Skylab, plus large chunks of the space station’s remains in the Municipal Museum where, of course, you can also buy Skylab T-shirts, stickers and other souvenirs.