The James Webb Space Telescope (JWST) used its near infrared spectrometer (NIRSpec) to examine Ganymede’s surface in unprecedented detail. The observations revealed:
- Ganymede’s surface is dominated by two types of terrain: bright, icy terrains with grooves, and darker regions.
- The bright regions cover about two thirds of the surface, and the dark regions cover the rest.
- The darker regions are older, and also highly cratered.
- The presence of hydrogen peroxide (H2O2) around the north and south poles of Ganymede. This discovery marks the first time that hydrogen peroxide has been directly detected on this moon.
- Absorption lines of hydrogen peroxide at Ganymede’s poles indicate radiolysis of water ice by charged particles funneled by the moon’s magnetic field.
- Charged particles funneled along Ganymede’s magnetic field are preferentially altering the surface chemistry of its polar caps.
Ganymede is the largest moon in our solar system. It’s bigger than Mercury and Pluto. Ganymede is about 665,000 miles (1.07 million kilometers) from Jupiter.
The JWST took a closer look at Ganymede, the moon that’s kind of like a planet, to understand its surface better. Ganymede is basically a planet, except it doesn’t orbit the Sun. If it did orbit the Sun instead of Jupiter, it would be indistinguishable from a planet
Here are some other interesting facts about Ganymede:
- Ganymede is one of Jupiter’s four Galilean moons, discovered by Galileo in 1610.
- Ganymede is named after a Trojan prince in Greek mythology.
- Ganymede’s magnetic field causes auroras, or bright ribbons of glowing gas, that circle the moon’s poles.
- Ganymede’s magnetic field is typically found on planets like Earth.
- Ganymede’s surface temperature is – 163 degrees C.
- Ganymede is the largest Solar System object without an atmosphere.
- Ganymede’s composition is roughly half rock and half water ice by mass.
- Ganymede’s orbital period is 7.16 days.
- Ganymede’s mass is 1.48 x 10^23 kg (2.0 Moons).
Here are some other interesting facts about Jupiter’s moons:
- Europa The second moon of Jupiter, and the smallest of the Galilean moons. Europa’s surface is covered by what appears to be a cracked sheet of water ice, which may cover a thick ocean. Europa’s surface temperature at the equator never rises above minus 260 degrees Fahrenheit (minus 160 degrees Celsius). At the poles of the moon, the temperature never rises above minus 370 F (minus 220 C).
- Callisto The outermost Galilean moon. Callisto is one of the largest and most heavily cratered satellites in the solar system. The surface is very icy and dates back four billion years.
- Metis The closest moon to Jupiter at a distance of 128,000 km. It is roughly 40 km in diameter, tidally-locked, and highly-asymmetrical in shape. It was not discovered until the 1979 flyby of Jupiter by the Voyager 1 space probe.
- Io Has a lot of active volcanoes and is covered with sulfur
Europa is considered the best place to find life in our solar system. It’s thought to have a vast ocean of water beneath its icy surface. The ocean is shielded from harmful radiation, and contains twice the water found in Earth’s oceans. The liquid water is in direct contact with the silicate mantle.
Europa is one of the two Jupiter moons most likely to potentially support life. Ganymede is the other.
Some astronomers believe that Ganymede is more similar to Earth than Venus or Mars. Ganymede has Earth-like faults, and its younger regions have grooves and ridges that are thought to have been formed by tectonic forces similar to those on Earth. Ganymede is also less than half the size of Earth.
Europa is also similar to Earth in several ways:
- It has an iron core, a rocky mantle, and an ocean of salty water.
- It has an estimated ocean depth of 40 to 100 miles (60 to 150 kilometers).
- It has a gravity that’s only about 13 percent of Earth’s.
- It’s considered one of the best candidates for habitability because the liquid water is in direct contact with the silicate mantle
Ganymede’s surface is made up of rock and ice. It has a core of metallic iron, a layer of rock, and a thick crust of mostly ice. The surface includes:
- Mountains
- Valleys
- Craters
- Lava flows
- Grooves
- Bumps that may be rock formations
- Polar caps likely composed of water frost
The darker regions are older and more heavily cratered. The largest dark region is named Galileo Regio and is almost 2000 miles in diameter. The craters on Ganymede are flatter than those on the Moon and Mercury, probably due to the relatively weak nature of Ganymede’s icy crust.
Humans couldn’t live on Ganymede in the same way they live on Earth. Ganymede has almost no atmosphere, so it’s exposed to radiation from space, the sun, and Jupiter. It’s also very cold, with surface temperatures ranging from negative 300 Fahrenheit to negative 180 Fahrenheit.
However, Ganymede is one of only two Jovian moons where surface settlements would be feasible. It has its own magnetosphere, which shields it from some of Jupiter’s radiation. Ganymede receives about 0.08 Sv of radiation per day.
Ganymede could be terraformed. It has a silicate crust that’s fragile and can’t support much weight. The ice crust could be melted into water and filtered to sustain large-scale agriculture
With current technology, it’s not possible to land on Ganymede. However, there are plans to land a probe on Ganymede in the next 20 years. The Russian government allocated funds for the project in 2013, but it was shelved in 2017 due to its complexity and cost.
The Juno spacecraft has passed within 500 miles of Ganymede, but it’s not equipped for a landing. The JUICE mission is expected to orbit Ganymede in 2034( source google)
Several spacecraft have explored Ganymede, including:
- Pioneer 10: The first probe to approach Ganymede in 1973
- Voyager 1 and Voyager 2: Refined measurements of Ganymede’s size
- Galileo: Discovered Ganymede’s magnetic field in 1996
- Juno: Took detailed photographs of Ganymede in June 2021
- Hubble Space Telescope: Found evidence of an underground saltwater ocean and a thin oxygen atmosphere
The European Space Agency’s (ESA) Jupiter Icy Moon Explorer (JUICE) mission is the only current mission planned for Ganymede. JUICE launched on April 14, 2023, and is expected to arrive in the Jovian neighborhood in December 2031. It’s slated to fly past Ganymede in 2029 and begin orbiting it in 2032. ( source google)
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