Ganymede, Titan, looking for life “star of hope”

On Earth, there is almost life where there is water from the clouds above the surface to the depths of the earth’s crust. “Living by water” is the basic rule that human survival and development has been following since ancient times, which is why scientists in the search for life in extraterrestrial objects, usually “water-by-water”, focusing on water-based celestial bodies.

Data from the Galileo probe show that there is a huge ocean under the icy shell of Ganymede. Photo: USSpace

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According to the United States Space Network recently reported that there is a large amount of liquid water in the outer solar system, which lurks under the satellite ice shell. The most notable of these are Saturn’s moons, Titan’s Enceladus and Jupiter’s Europa, which are believed to have contact with the core in their subsurface oceans, allowing complex chemical reactions to occur.

Many scientists believe that there may be tiny creatures swimming in the dark, cold oceans of Ganymede and Titan, and they hope to send robots to the subterranean oceans of these satellites to search for “traces” of life. “It’s the culmination of a water-by-water drama,” Emily Kolonik, a planetary protection engineer at NASA’s Jet Propulsion Laboratory (JPL), told “

Go to Europa

The Europa Express Sailing mission to visit Ganymede is currently in the process of being launched in the mid-1920s. Once in Jupiter’s orbit, it will fly dozens of times over Europa, map its ocean features, study its ice in detail, and perform other missions. In addition, the European Space Agency’s (ESA) Jupiter Ice Moon Probe (JUICE) will study Ganymede, Ganymede and Jupiter itself. JUICE is Jupiter’s orbiter and is scheduled to launch in 2022.

The Europa Express mission will pave the way for a future Ganymede lander, which the U.S. Congress has instructed NASA to develop is still in the conceptual research phase. It will go 10 cm below the surface of Ganymede, looking for life. At this depth, NASA officials say, any biomolecule would be protected from radiation by the ice above it.

Scientists point out that most of the biomolecules on Ganymede may eventually originate from its wide ocean, which has about twice as much water as all of the Earth’s oceans. So Kolonik and others want to send a life-searching robot, which could be a swimming “squid” or a robot that can roll along the ice of the ocean.

Drilling systems are critical.

However, Ganymede’s ice shell is 15-25 kilometers thick, so the expedition must carry a powerful rig. NASA is trying to promote this advanced technology through the Europa Science Exploration Underground Access Mechanism (SESAME) program. SESAME’s ultimate goal is to develop a nuclear-powered “drilling system” that can drop about 15 kilometers in three years of operation. The “drilling system” will be no more than 200 kg and will be transported from the lander to the surface of Ganymede, in addition to providing relays for communication between the drilling equipment and the Earth.

Currently, JPL, Georgia Institute of Technology, Johns Hopkins University, Stone Aerospace and Bee Robotics are all working on various aspects of this large system, all of which are funded by SESAME.

Johns Hopkins University focuses on how drillers communicate with landers; Bee Robotics is developing a hybrid drilling system that uses underwater-heated Life Search Systems (SLUSH), which uses both thermal and mechanical methods to cut through the ice.

“The biggest problem is heat, and if you don’t cool it out in some way, the drill will overheat,” said Chris Zachny, director of Bee Robotics. “

Of course, there are other potential difficulties. Once the drill is drilled deep enough, communication between the drill and the lander may be difficult to carry out through the tether. With that in mind, researchers are studying the possibility of deploying disc-shaped modems behind a drill when it drops, says Tom Kwik of JPL.

In addition, disinfection of drillers and marine detection robots is critical, which minimizes the contamination of the environment on Ganymede by the Earth’s microbes. However, given the complexity of the hardware, this sterilization will be difficult to achieve.

Sam Howell, a co-researcher at SESAME, says most of the technology required for the drill could take 10 to 15 years to get ready. If developed from now on, it may not be until the late 1930s to visit Ganymede to explore its oceans, “the Ganymede expedition mission is a real risk, but it is worth the risk”.

Expedition to Titan

The sea of Titan may be more “amiable” than That of Ganymede, but some of the strategies used by Expedition Europa can also be used in Titan.

There are many giant “tiger-print” fissures in the Titan Antarctic region, where dozens of geysers spray water ice, organic molecules and other material into space, creating plumes that make up Saturn’s E-ring.

The geyser’s material is likely to come from Titan’s oceans, so these tiger-print fissures could be the entrance to the detector, thus eliminating the need to drill ice into the ocean, and some scientists and engineers are developing technology that facilitates the fissures.

A team at JPL is working on the “EELS” device, a four-metre-long snake-like robot that will circle down the tiger-print fissure until it reaches liquid water. The researchers explained that a long rope would connect the EELS to a lander on the ground, powering the ocean “explorers.”


Jason Hofgartner of JPL and colleagues said: “This ‘flagship’ mission will be the search for life on titan’s surface, in the ice crust and deep in the ocean underground, and this could be the best opportunity in astrobiology in the next decade. “

The “flagship” missions are NASA’s “highest-paid” categories of missions, such as the Curiosity Mars rover and the Cassini Saturn probe, all of which are “flagship” projects, which typically invest more than $1 billion.

Even if NASA ultimately failed to approve the mission, scientists are studying ways to sample the ocean indirectly. Previously, Cassini has flown over Titan’s plume several times, and future life-searching probes can do just that. The Cassini mission ended in September 2017. Several research groups have submitted design ideas for the Titan plume sampling mission, but NASA has yet to finalize an in-depth research and development project.

What surprises will these two cold, frozen moons bring to humanity? We’ll see.