The US-led Cassini probe to Saturn will destroy itself in the coming hours.The $4bn (£3bn) mission is ending 13 years of discoveries at the ringed planet by ditching itself in the atmosphere.With an expected entry speed of 120,000km/h (76,000mph), the spacecraft will rapidly be torn to pieces.
Scientists, however, hope to gain new information on the chemical composition of Saturn’s gases just before Cassini loses radio contact with Earth.
That is likely to occur just after 04:55 local time here at mission control – the Nasa Jet Propulsion Laboratory (JPL) in Pasadena, California (11:55 GMT; 12:55BST).It will be a bittersweet moment for the hundreds of mission researchers who have come from all over the world to be in the Los Angeles County town for the occasion.
Former US space agency chief scientist Ellen Stofan is part of the probe’s radar instrument group.
“We’ve done amazing science; it’s an amazing team. And I think we can celebrate that we’ve really eked every little bit of science that we could out of the Cassini spacecraft. But then it’s what’s next?
“We want to go back to Titan, we want to go back to Enceladus; there’s so much we don’t know about the interior of Saturn, so people have talked about Saturn probe missions. There’s a lot more to be done,” she told the BBC.
Cassini has revolutionised our understanding of the sixth planet from the Sun.It has watched monster storms encircle the globe, and witnessed the delicate interplay of ice particles move through its complex ring system.
And then there are those remarkable moons Titan and Enceladus, which host vast bodies of liquid water beneath their icy shells and where scientists say conditions may be favourable for simple life to exist.
But after taking hundreds of thousands of pictures and other measurements, it is now time for Cassini to retire.
It is down to its last few kilos of fuel and the US space agency does not want an uncontrolled probe wandering aimlessly around the outer Solar System. The ship is to be scuttled.
This was the best solution,” said Earl Maize, the Nasa Cassini project manager. “We could have parked Cassini way outside the rings, and outside the icy moons. We could even have sent it away from the Saturn system but no-one saw any scientific benefit in that.”
In contrast, the “death plunge”, as it has become known, offers a way to get some unique data.
By tightening the probe’s orbit so that it flies in between the rings and the planet’s atmosphere, which it has been doing since April, researchers have gained new insights on the age of the rings, on the internal structure of Saturn and on the composition of its gas envelope.
The scientists will now take the ultimate step in these investigations by driving Cassini straight into the planet.Eight instruments will be switched on and reporting conditions for as long as is possible.This could be 60 seconds; with luck it will be a bit longer. But at some point the probe will not be able to maintain stability as gases rush over its irregular shape.
Cassini will start to tumble, break apart and melt – its materials dispersing to become a near-indistinguishable part of the planet it has worked so hard to describe.