Today's perspective
Scientists have carried out a long-term and continuous exploration of Mars, and sent several "messengers" to Jupiter, Saturn, Mercury, and Venus, respectively. They have discovered many secrets of these planets. Only Uranus and Neptune, so far only "Traveler 2" The detector was visited in the 1980s. The two blue ice giants are the farthest planets in the solar system and the least mysterious and most mysterious planets.
Now, as a rare "planet of the planet" approaches, more and more scientists are proposing to send probes to Uranus or Neptune. They believe that exploring these two ice giants will lead to many new research areas, including the study of Uranus' planetary rings, planetary atmospheres, planetary satellites and oceans, and further reveal the hidden mysteries of the solar system's edges.
The picture shows the photo of Uranus.
"Blue Demon Girl" in the Solar System
Uranus is a marbled pale blue planet suspended in the dark and icy deep space, 2.9 billion kilometers from the sun. Like Saturn, Uranus has planetary rings. In the depths of space 4.5 billion kilometers from the sun, Neptune inhabits.
Astronomers see Uranus and Neptune as "twin" because they are similar in size and mass. But Lavit Helleder, a planetary scientist at the University of Zurich in Switzerland, says no one knows exactly how similar they are, nor how they are made up and how they are formed.
Existing models are difficult to explain the internal structure of these two planets, nor can it explain why Neptune, which is more distant from the sun, seems to be hotter than Uranus, which is closer to the sun-data provided by Voyager 2 shows that Uranus surface temperature It is minus 224 degrees Celsius and is the coldest planet in the solar system; Neptune's surface temperature is minus 214 degrees Celsius.
Hellerd said that everyone believes that the two celestial bodies are made of water or ammonia ice, "but the truth is still unknown", and a detector needs to be sent to find out.
Hannah Wickford, an exoplanet scientist at the University of Bristol, said that a major mission to explore ice giants would also benefit exoplanet research. Because about 40% of the known exoplanets are about the size of ice giants, the exploration of these two ice giants in the solar system will help us to further understand the size and atmosphere of these exoplanets, thereby revealing their formation and evolution process.
Visiting either of these two ice giants will yield fruitful results. Studies have shown that while sending a probe to visit two planets is feasible, the cost of doing so is too high.
If one of the two is chosen, some scientists believe that a probe should be sent to visit Neptune, because its largest satellite Triton Triton is active in geological activity, and it may have one that may be composed of liquid water. Underground ocean.
But Mars Hofstadter, a planetary scientist at NASA's Jet Propulsion Laboratory, believes that Uranus is more exotic than Neptune because Uranus' magnetic field is tilted relative to the planet's axis of rotation, which challenges existing scientific models. In addition, the launch window of Uranus a little later makes the exploration of this planet more practical.
Gravity Slingshot Effect of "Planet Lianzhu"
Scientists said that in addition to Neptune and Uranus, the pair of "blue demon girls" themselves are full of mysterious temptations, the rare "planet renju" phenomenon between these two planets and Jupiter will appear in the early 1930s. "Planet Lianzhu" means that the planets are all on the same side of the sun and are aligned in a straight line.
By then, the spacecraft can take advantage of this phenomenon and use Jupiter's gravitational slingshot effect on the way to the planet to shorten the travel time and reach its destination faster. In addition, the use of the gravitational slingshot effect can also reduce the fuel consumption of the detector, enabling the spacecraft to carry a full set of scientific instruments.
To take advantage of this rare moment, a probe to Neptune needs to be launched around 2031; a probe to Uranus needs to be launched in the mid-1930s.
Hofstadter said that the above two time periods were "the right timing to launch, and the opportunity is not lost."
Missed opportunity will wait another ten years
Still, many people worry that time is too late. For NASA, such multi-billion dollar "flagship" missions usually take 7-10 years to prepare, and NASA will prioritize the missions as determined in the Planetary Decade Survey to be released in 2022. To consider which projects to approve, missions to Neptune or Uranus will face competition for proposals such as taking samples from Mars or exploring Venus.
Fabio Fawata, head of strategy, planning and community coordination at the European Space Agency (ESA), said that as far as space is concerned, "it is like sending a probe the day after tomorrow". The ESA is working on two important missions and is expected to launch in the early 1930s. As a result, Voyage 2050 proposed to visit the ice star, and ESA was unable to launch a probe from this launch window. "Traveler 2050" is ESA's next long-term space exploration program. All selected projects will be launched between 2030 and 2050.
He added that, as an alternative, ESA could participate in NASA-led missions if the United States agreed. Both agencies can send lighter, lower-cost tasks, such as flying over one of the ice stars. This will also provide scientists with valuable data, but it will not provide the comprehensive data that scientists hope.
If the launch window of the 1930s is missed, scientists will have to wait another ten years for the next "planetary bead" phenomenon or rely on more powerful launch systems, such as NASA's "Space Launch System" (SLS) , But the technology is still in the research and development stage.
Leah Fletcher, a planetary scientist at the University of Leicester, said that humans have carried out in-depth explorations of Mars, Venus, Saturn, Jupiter, etc., but "Uranus and Neptune are unique, and we have not finished exploring them. The first stage. "
Every human visit to the ice giant is a voyage into the unknown world. Although the probe will be too fast when it arrives there, it can only stay for a few hours within the planetary range, but the data collected during these hours also lets us begin Learn the secrets hidden in the marginal space of the solar system.
Our reporter Liu Xia