Planet Earth is parting company with an asteroid that’s been tagging along as a "mini moon" for the past two months.
The harmless space rock will peel away on Monday, overcome by the stronger tug of the sun’s gravity. But it will zip closer for a quick visit in January.
NASA will use a radar antenna to observe the 33-foot asteroid then. That should deepen scientists’ understanding of the object known as 2024 PT5, quite possibly a boulder that was blasted off the moon by an impacting, crater-forming asteroid.
While not technically a moon — NASA stresses it was never captured by Earth’s gravity and fully in orbit — it’s "an interesting object" worthy of study.
The astrophysicist brothers who identified the asteroid’s "mini moon behavior," Raul and Carlos de la Fuente Marcos of Complutense University of Madrid, have collaborated with telescopes in the Canary Islands for hundreds of observations so far.
Currently more than 2 million miles away, the object is too small and faint to see without a powerful telescope. It will pass as close as 1.1 million miles of Earth in January, maintaining a safe distance before it zooms farther into the solar system while orbiting the sun, not to return until 2055. That’s almost five times farther than the moon.
First spotted in August, the asteroid began its semi jog around Earth in late September, after coming under the grips of Earth’s gravity and following a horseshoe-shaped path.
By the time it returns next year, it will be moving too fast — more than double its speed from September — to hang around, said Raul de la Fuente Marcos.
NASA will track the asteroid for more than a week in January using the Goldstone solar system radar antenna in California’s Mojave Desert, part of the Deep Space Network.
Current data suggest that during its 2055 visit, the sun-circling asteroid will once again make a temporary and partial lap around Earth.
A NASA spacecraft is ready to set sail for Jupiter and its moon Europa, one of the best bets for finding life beyond Earth.
Europa Clipper will peer beneath the moon’s icy crust where an ocean is thought to be sloshing fairly close to the surface. It won’t search for life, but rather determine whether conditions there could support it. Another mission would be needed to flush out any microorganisms lurking there.
"It’s a chance for us to explore not a world that might have been habitable billions of years ago, but a world that might be habitable today — right now," said program scientist Curt Niebur.
Its massive solar panels make Clipper the biggest craft built by NASA to investigate another planet. It will take 5 1/2 years to reach Jupiter and will sneak within 16 miles of Europa's surface — considerably closer than any other spacecraft.
Liftoff is targeted for this month aboard SpaceX’s Falcon Heavy rocket from NASA’s Kennedy Space Center. Mission cost: $5.2 billion.
One of Jupiter’s 95 known moons, Europa is almost the size of our own moon. It's encased in an ice sheet estimated to be 10 miles to 15 miles or more thick. Scientists believe this frozen crust hides an ocean that could be 80 miles or more deep. The Hubble Space Telescope has spotted what appear to be geysers erupting from the surface. Discovered by Galileo in 1610, Europa is one of the four so-called Galilean moons of Jupiter, along with Ganymede, Io and Callisto.
What type of life might Europa harbor? Besides water, organic compounds are needed for life as we know it, plus an energy source. In Europa’s case that could be thermal vents on the ocean floor. Deputy project scientist Bonnie Buratti imagines any life would be primitive like the bacterial life that originated in Earth’s deep ocean vents. "We will not know from this mission because we can’t see that deep," she said. Unlike missions to Mars where habitability is one of many questions, Clipper’s sole job is to establish whether the moon could support life in its ocean or possibly in any pockets of water in the ice.
When its solar wings and antennas are unfurled, Clipper is about the size of a basketball court — more than 100 feet end to end — and weighs nearly 13,000 pounds. The supersized solar panels are needed because of Jupiter’s distance from the sun. The main body — about the size of a camper — is packed with nine science instruments, including radar that will penetrate the ice, cameras that will map virtually the entire moon and tools to tease out the contents of Europa’s surface and tenuous atmosphere. The name hearkens to the swift sailing ships of centuries past.
The roundabout trip to Jupiter will span 1.8 billion miles. For extra oomph, the spacecraft will swing past Mars early next year and then Earth in late 2026. It arrives at Jupiter in 2030 and begins science work the next year. While orbiting Jupiter, it will cross paths with Europa 49 times. The mission ends in 2034 with a planned crash into Ganymede — Jupiter’s biggest moon and the solar system's too.
There’s more radiation around Jupiter than anywhere else in our solar system, besides the sun. Europa passes through Jupiter’s bands of radiation as it orbits the gas giant, making it especially menacing for spacecraft. That’s why Clipper’s electronics are inside a vault with dense aluminum and zinc walls. All this radiation would nix any life on Europa’s surface. But it could break down water molecules and, perhaps, release oxygen all the way down into the ocean that could possibly fuel sea life.
Earlier this year, NASA was in a panic that the spacecraft's many transistors might not withstand the intense radiation. But after months of analysis, engineers concluded the mission could proceed as planned.
NASA’s twin Pioneer spacecraft and then two Voyagers swept past Jupiter in the 1970s. The Voyagers provided the first detailed photos of Europa but from quite a distance. NASA’s Galileo spacecraft had repeated flybys of the moon during the 1990s, passing as close as 124 miles. Still in action around Jupiter, NASA’s Juno spacecraft has added to Europa’s photo album. Arriving at Jupiter a year after Clipper will be the European Space Agency’s Juice spacecraft, launched last year.
Like Europa, Jupiter’s jumbo moon Ganymede is thought to host an underground ocean. But its frozen shell is much thicker — possibly 100 miles thick — making it tougher to probe the environment below. Callisto’s ice sheet may be even thicker, possibly hiding an ocean. Saturn’s moon Enceladus has geysers shooting up, but it’s much farther than Jupiter. Ditto for Saturn’s moon Titan, also suspected of having a subterranean sea. While no ocean worlds have been confirmed beyond our solar system, scientists believe they’re out there — and may even be relatively common.
Like many robotic explorers before it, Clipper bears messages from Earth. Attached to the electronics vault is a triangular metal plate. On one side is a design labeled "water words" with representations of the word for water in 104 languages. On the opposite side: a poem about the moon by U.S. poet laureate Ada Limon and a silicon chip containing the names of 2.6 million people who signed up to vicariously ride along.
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