Heading for Uranus | The Press

The two “ice giants”, Uranus and Neptune, are the only planets in the solar system not to have been visited by a probe dedicated to them. NASA has just decided to remedy the situation.

Mathieu Perreault
The Press

The time has come

In 2011, in NASA’s second ten-year plan for planetary exploration, it was considered a lower priority than Mars. But in the third plan, presented in the spring, Uranus found itself at the top of the list.

NASA has decided that the time has come to take an interest in the seventh planet of the solar system, the only one with Neptune never to have been studied by an orbiter or a lander. “We have pictures of Voyager 2, which passed close to Uranus in 1986, and that’s it,” explains Léa Griton, from the Paris Observatory. She works on simulations of the Iranian magnetosphere and on the future NASA probe.

Uranus is the only planet in the solar system that spins perpendicular to its axis of rotation around the Sun. In comparison, the Earth is tilted only 23 degrees from its solar orbit. “Uranus’ magnetic field is very dynamic, it changes a lot over time, sometimes in the same day,” says Ms.^me Grito. On Earth, “excursions” (or rapid instabilities) of the magnetic field only occur every 50,000 to 100,000 years.

Odinus

Uranus is an “icy giant”, like Neptune. An American study published last year in Nature Physics suggested that these two planets could harbor liquid “superionic ice”.

It is for this reason that astrophysicists have long hesitated between two approaches to exploring Uranus. “We don’t have models to explain the physics of Uranus,” says Diego Turrini, of the Italian National Institute of Astrophysics in Turin. So it will be important to validate the data with Neptune. In 2013, Mr. Turrini designed the twin probes project Odinus to Neptune and Uranus, which never saw the light of day. Neptune is located 50% further than Uranus, 30 astronomical units (AU, the distance between the Earth and the Sun) from the Sun.

dusty rings

Despite its antediluvian technology, Voyager 2 reveals more secrets of Uranus. An astrophysicist from the University of Idaho recently announced that the amount of dust in some of its rings is increasing, thanks to a reanalysis of data from the probe launched in 1977. the power of today’s computers,” says Matthew Hedman, who presented his findings in early October at a meeting of the American Astronomical Society.

Triton

The other important motive for exploring both Neptune and Uranus is the Neptunian moon Triton. “It’s the only moon that spins the opposite of the other moons around its planet,” Turrini says. It is thought to be because it formed in the Kuiper Belt and was captured by Neptune. It’s sort of a cousin of Pluto. »

Exploring Triton would make it possible to better understand the “chaotic” hypothesis of the formation of the planetary system. “Until the turn of the millennium, planets were thought to have formed where they are now,” says Turrini. But several studies have shown that Jupiter formed much further away. And it is predicted that Mercury will disappear in a very long time. These planetary migrations have surely influenced the formation of life on Earth. »

Shakespeare

Uranus was discovered in the 18th^e century by a British musician of German origin, William Herschel. “He was a genius at getting funding for his research,” says Ms.^me Grito. He first named the planet George, in honor of King [du Royaume-Uni]. »

This choice of popular names in his adopted country extended to the two Uranian moons discovered by Herschel, Oberon and Titania, names of characters from the Dream of a summer night of Shakespeare. Subsequently, most of Jupiter’s other 27 moons, 10 of which were discovered with Voyager 2, have been given Shakespearean names. “To have Romeo in orbit around Uranus, I think it’s fantastic,” says M^me Grito. Herschel also demanded that the royal pension which rewarded his discoveries also be paid to his sister and collaborator Caroline. “She was the first woman paid as a researcher,” says Ms.^me Grito.

Uranus in fiction

Science fiction rarely addresses Uranus and Neptune. “There is much less interest in ice giants than in gas giants in the literature,” explains Geoffrey Landis, an electrical engineer at NASA. Mr. Landis, also a science fiction author, published in 1999 the short story Blue Abyss, where explorers at the controls of individual submarines discover life on Uranus. “One of the reasons is that it is difficult to imagine life on Uranus, so far from the Sun. »

In Blue Abyss, the fish that inhabit the Uranian superionic ocean feed on particles formed by a process a million times less efficient than photosynthesis, the basis of life on Earth. Uranus was the subject of only one film, in 1962, where extraterrestrial life takes control of the minds of astronauts.