On September 29, NASA’s Juno probe will perform the closest flyby of icy moon Europa to Jupiter in more than 20 years as the spacecraft embarks on a mission to explore Europe’s ice for pockets of liquid water.
Europa It has a global ocean under a hard crust of ice, making this moon one of the most interesting places in the world Solar System to me Searching for extraterrestrial life and one of The priorities of astrobiologists. Although Juno won’t be able to tell us whether Europa harbors alien life, it will teach us more about the moon’s icy crust, such as how dense it is and whether there are any subsurface pockets of liquid water that could reach the surface.
Juno arrived in Jupiter July 2016, its mission focused on Buyer’s Atmosphere Studyfrom the heights of brown cloud tops to the depths of cloud layers hundreds of miles down, as well as learning about the gas giant’s strong magnetic field and internal structure down to its core.
In 2021, NASA granted Juno a mission extension and gave it a new goal: to study some of it Jupiter’s Moons. In June 2021, the spacecraft flew 645 miles (1,038 kilometers) from Ganymede, with a diameter of 3,273 miles (5,268 km), is the largest moon in the solar system. Next, it will be Europa’s turn, with Juno set to advance past the Moon just 220 miles (355 km) above Europa’s surface. Juno will not see the entire moon, but rather a small part of the surface. However, Juno’s cameras have a wide field of view – a bit like a smartphone camera – allowing the spacecraft to capture more landscapes than a regular camera can.
staring under the ice
Juno’s work on Europa is considered an upcoming “exploration mission” for NASA Europa clipper mission, Scott Bolton, associate vice president for the Division of Space Science and Engineering at the Southwest Research Institute and principal investigator for the Juno mission, told Space.com. “But we still do a lot of science in Yoruba.”
Key to this science will be Juno’s Microwave Radiometer (MWR). “This is a new kind of instrument that we invented to see what’s under Jupiter’s clouds,” Bolton said. “But we can apply the same tool to an icy satellite and see the ice a little bit.”
MWR operates at six wavelengths and can detect thermal emission from beneath the icy surface. How deeply this emission is detected depends on the level of impurities in the ice. The purer the ice, the deeper the ice the MWR can “see”.
Although the results from Juno Ganymede flyby Bolton revealed that when Juno brought out the MWR at Ganymede, the instrument confirmed that the supermoon’s icy crust was very thick.
Europe may be a different story, at least at some points on the moon. Scientists hope one day to drill through the ice, in the moon’s dark subterranean ocean. The ice crust is expected to be 19 miles (30 km) deep, at least in most areas, but the ice crust may be thinner in some areas.
Previous missions that depicted Europa – the Voyager 1 And the Voyager 2 spacecraft and Galileo blindly – It was found that parts of the moon’s surface were stained with materials that appear to have been washed away from below. Juno’s infrared camera and spectrometer will analyze the composition of this material to determine if it is made of salts or organic molecules.
One theory is that Pockets of water can form underground, either by liquid rising through the ice crust, or by melting ice in the crust, possibly as a result of pressures imposed on it by Jupiter’s gravitational tides. The MWR should be able to tell if there are any water pockets close to the surface.
“When we were developing Juno, we didn’t really think about getting close to icy satellites; we were totally focused on Jupiter,” Bolton said. “Now that we look at the moons for our extended mission, it becomes clear that the microwave radiometer works incredibly beautifully on icy bodies as well as gas giants, so I think it will become the dominant backbone of planetary exploration in the future. “
Regarding the possibility of liquid water being close to the surface is controversial Evidence of erupting heaters of water that climbs high above the surface and into space. In 2013, Hubble Space Telescope I discovered plume-shaped clouds of hydrogen and oxygen (which, when combined, make water) and in 2016 saw the potential silhouettes of these plumes. Scientists looking at archived data from the Galileo spacecraft found they measured slight disturbances in Jupiter’s magnetosphere near Europe that could be the result of charged particles in the plume deflecting the giant planet’s magnetic field.
In 2021, scientists Find enough water vapor It was launched over Europe to fill an Olympic-sized swimming pool in just minutes. However, how the water vapor got there is still uncertain, as scientists have so far failed to confirm the existence of geysers.
Could Juno make the first confirmed discovery of a geyser in flight? “It’s a long shot,” Bolton said. “If the plumes are there, we have to get lucky and make them fly as we fly through, and they should be somewhere we’re just looking forward to.”
However, even if Juno does not detect a plume in action, the spacecraft may see a geologic feature on the surface emitting water vapor, similar to “tiger stripes” on me Saturnicy moon Enceladus that fires their water heaters. Instead, Juno’s navigation cameras will look for icy particles drifting back to Europa’s surface, reflecting and scattering light.
Juno’s polar orbit around Jupiter, flying over North Pole Then the south pole, meaning it will approach Europa from a high mile, giving spacecraft images of the moon’s polar regions for the first time. In contrast, previous missions embraced the level of the moons and focused on their equatorial regions. Juno’s orbit also means that this is the spacecraft’s only chance of observing Europa up close.
“What’s happening is that Juno’s orbit is now shifted by Jupiter’s gravitational field,” Bolton said. “We’ve always crossed the equator, but the closer we get to Jupiter, the point at which we cross the equator moves inward.”
Juno crossed the equator of Jupiter at a distance of Ganymede – 665,000 miles, 1.07 million km in the summer of 2021. Now, the spacecraft crosses the equator of Jupiter at a distance of Europa – 383,000 miles (617 thousand km). And in December 2023 and February 2024, Juno will cross the equator of Jupiter at the distance of its volcanic moon. Io – 262,000 miles (422,000 km) – and perform two close flybys, both within a range of 932 miles (1,500 km).
Juno’s extended mission will run until 2025, at which point scientists will have to make an assessment: whether the spacecraft has enough propellant to continue pointing its antenna toward a land And it’s in good enough shape to last, or whether the job is done.
“I imagine NASA would receive another extension if the spacecraft was in good health,” Bolton said.
The main issue is radiation. Juno’s orbit around the giant planet is elliptical, and every time it reaches perihelion – its closest point to Jupiter – it receives a huge dose of radiation from the charged particles trapped in it. Jupiter’s strong magnetosphere The surface of the planet’s moons is routinely touched. To resist this radiation, Juno was built “like an armored tank with armor,” Bolton said, “but in the end, our armor wouldn’t hold up, to use it.” Star Trek language, and the radiation will begin to damage Juno’s electronics.”
Juno’s encounter with Europa may be the only shot, but it won’t be the last spacecraft to visit Jupiter’s icy moons. The much-anticipated Europa Clipper mission from NASA is Scheduled to be released in October 2024 It will reach orbit around Jupiter in April 2030. Europa Clipper will make nearly 50 flights close to Europa to fully characterize the moon and follow Juno’s search for pockets of liquid water underground that could support life. Meanwhile, the European Space Agency’s icy Jupiter explorer (juice) in April 2023, to reach Jupiter in July 2031, on a mission to study Europe, Ganymede and Callisto.