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A relic from early spaceflight has likely returned to pay a brief visit to its home planet, according to months of sightings of a near-Earth object dubbed 2020 SO.
2020 SO entered what scientists call the Earth’s Hill sphere, where Earth’s gravity governs the behavior of objects, on November 8, according to a NASA statement. Scientists say the object will quietly loop twice around the Earth before slipping away to resume its way around the sun in March.
But although scientists first spotted it in September during surveys to identify asteroids, the object soon appeared to be something entirely different – the top stage of a rocket from a 1966 NASA lunar robotic mission called Surveyor 2. And that would indeed make a space junk with a fairly rich history.
“If it’s the top tier of the Centaur,” said Alice Gorman, an archaeologist specializing in spaceflight heritage, “it’s that object in itself, it’s that rocket stage, but it’s also related to all these other things. “
Related: The Strange Story of 2020 SO: How an asteroid turned into a rocket junk and the NASA scientist who figured it out
This piece of metal left Earth on September 20, 1966, perched on top of a first floor of the Atlas D and carrying at its end a spacecraft called Surveyor 2. Three days later, this spacecraft inadvertently crashed on the moon. The metal cylinder that had delivered it, meanwhile, passed in front of our heavenly neighbor and settled down to circle the sun more or less in tandem with our home planet.
And apparently it’s been 54 years. Throughout these years, the successors of the Centaur have proliferated, launching countless rockets off Earth and on a multitude of orbital and planetary exploration missions.
A long career for a simple design
The Centaur rocket stage, in one form or another, has played a key role in space exploration for essentially the entire history of spaceflight. It is the result of a partnership between NASA (and its predecessor) and the commercial sector in the late 1950s and first launched in March 1962.
The stage was a vital development in the rocket as it was the first successful design to rely on dangerously finicky yet light and efficient liquid hydrogen, according to a Story published by NASA of the component. Centaur’s success established that liquid hydrogen could be used safely, helping the United States catch up with the Soviet Union during the Space Race.
But despite this leading role, the upper floor of the Centaur is deceptively simple. “It’s a really simple rocket,” Gorman said. “It’s like a big fuel tank with two rocket engines.” And it’s flexible: While over the years it has flown most often with the Atlas first stage, it can join a range of rockets. In the 1980s, it was even adapted for launch inside NASA’s space shuttle to guide satellites to their proper orbits, although it never ended up flying in that configuration.
Only one version of the Centaur Stage continues to fly today, built into the United Launch Alliance’s Atlas V rockets, but it is also designed in the company’s future Vulcan Centaur rocket, due to maybe launch next year.
The Centaur’s long history is a good reminder of the transient, mix-and-match nature of every rocket, Gorman said. Launchers spend much more time as components, often spread over large geographic areas, than as a single unit.
“In our mind we have this vision of the rocket, which is the big thorny thing on the launch pad, but this rocket only exists for a short time,” she said. “It’s assembled in the week before launch … it launches and separates and leaves itself in pieces.”
Watch the moon
The particular Centaur bit now temporarily rattling around the Earth was part of a vital suite of missions that paved the way for the Apollo program by proving he was safe to land on the moon, although his particular spaceship failed.
Between 1966 and 1968, the United States launched seven missions dubbed Surveyor, each designed to land on the moon. Overall, the program has been a success; Surveyor 2 itself was the only exception when it crashed into the lunar surface.
Its predecessor probe, Surveyor 1, made the first American soft landing on the moon.
“Landing on the moon was really exciting; it’s a bit like landing on Mars these days,” Paul Chodas, head of NASA’s Center for Near-Earth Object Studies at the Jet Propulsion Laboratory in California, who saw the object detected during asteroid surveys and realized it was probably the Surveyor 2 Centaur, Space.com said. “It’s fascinating, especially because I remember these missions. Surveyor 1 was a very exciting landing on the moon – as a child I watched the moon through my telescope when it landed.
And the successful soft landing also provided vital evidence for the history Apollo 11 landing on the human moon three years later, Gorman said.
“There were sort of two theories about moon dust back then: one was that it was incredibly deep, so if you sent a human mission it would just sink into the dust, and the other was that the dust wasn’t that deep, “Gorman said. “So one of the things the surveyors did was prove that, at least in the places where the seven missions landed, that the dust was not a few feet deep, so it would be safe for a much heavier craft to land on the surface – quite significant in terms of the overall development of human spaceflight and lunar science. “
But while Surveyor 2 may not have lived up to its siblings, its Centaur may well be on its way to becoming the first orbiting the sun 1960s rocket body that scientists have rediscovered. Astronomers plan to observe the object to try to confirm the connection, but for Chodas, the trajectory is convincing evidence in itself.
“The fact that it can be very closely tied to the launch of Surveyor 2, which took place 54 years ago, is truly amazing,” Chodas said. “It’s kind of the first time I’ve been able to make such a strong association with a rocket launch from the 1960s.”
Email Meghan Bartels at [email protected] or follow her on Twitter @meghanbartels. follow us on Twitter @Spacedotcom and on Facebook.
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