Robotic space probes have proven themselves to be capable explorers, roaming the solar system, observing the galaxy, and pushing back the boundaries of the final frontier. Those looking for a return to the glory days of human space exploration will need patience. NASA is aiming for a human landing on Mars in the 2030s, though cynics might contend that a Mars mission has been “just over the horizon” for a generation. Private-sector efforts in the near term are limited to suborbital tourism. Fortunately, NASA, the European Space Agency, and groups from other countries are readying a variety of missions that should answer some of astronomy’s biggest questions, all while keeping human feet firmly on the ground. In this article, we review nine unmanned missions that will explore new frontiers in space over the next decade.

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Are Astronauts Obsolete

Robotic space probes have proven themselves to be capable explorers, roaming the solar system, observing the galaxy, and pushing back the boundaries of the final frontier.

Human spaceflight does have great sentimental appeal. Former U.S. astronaut and MIT professor Jeffrey Hoffman misses the old days. “When I was flying in the space,” he laments, “we were putting 40 astronauts a year, now we are putting four.” Those few astronauts are dispatched to the International Space Station for scientific research and in-flight maintenance.

Those looking for a return to the glory days of human space exploration will need patience. NASA is aiming for a human landing on Mars in the 2030s, though cynics might contend that a Mars mission has been “just over the horizon” for a generation. Private-sector efforts in the near term are limited to suborbital tourism.

For now, we will have to be content with robot missions. Fortunately, NASA, the European Space Agency, and groups from other countries are readying a variety of missions that should answer some of astronomy’s biggest questions, all while keeping human feet firmly on the ground.

TESS

The April 2018 launch of the Transiting Exoplanet Survey Satellite was a milestone for astronomers, who expect TESS to find as many as 20,000 planets orbiting nearby stars. This so-called planet hunter will detect its quarry by monitoring the brightness of 200,000 target stars; whenever a planet passes in front of the star, it will dim the star ever so slightly. It’s the same kind of observation performed until recently by the Kepler satellite, which discovered 2,343 exoplanets including 30 that were Earth-sized planets within their star’s habitable zone.

“TESS will also identify promising candidates for detailed follow-up by other powerful telescopes like Hubble and the upcoming James Webb Space Telescope to better understand these planets’ atmospheres,” said Natalia Guerrero, a TESS researcher at MIT.

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James Webb Space Telescope

The Hubble Space Telescope revolutionized astronomy in the 1990s, and astronomers have even higher hopes for its successor, scheduled to launch in 2020. As an infrared telescope with more than seven times the light-gathering ability as the Hubble, JWST will see more distant galaxies with greater detail, and its spectrograph will provide insight on the chemical makeup of far-off objects. The telescope will also feature coronagraphs that can block the direct light from a star so that the instruments can focus on the light reflected from adjacent objects such as extrasolar planets. Astronomers think JWST can answer a lot of their questions, but if the half-billion dollar instrument needs a repair, they’ll be out of luck: it will orbit around a gravitational node some 1.5 million km from Earth, far beyond the reach of any astronaut.

Osiris-REx

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The OSIRIS-REx mission is already underway (it was launched in 2016) but next month it will reach its target, the asteroid Bennu. The spacecraft will spend more than a year mapping the asteroid— not so hard, since it’s about 0.3 miles across—and then make a close enough pass to scoop up some soil with a robotic arm. If that daring maneuver works, the probe is scheduled to return to Earth in 2023. “For the first time we’ll bring back a sample of an asteroid,” said astronaut Jeffrey Hoffman. Private companies are also planning to visit asteroids, and even start mining them.

Mars 2020

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Humans have been sending robotic explorers to Mars since 1964, when Mariner 4 sent back the first close-up images of the Red Planet. The next visitor, scheduled for launch in 2020, will investigate Mars not from orbit, but over land and through the air. The one-ton rover, powered via a radioisotope thermoelectric generator rather than solar panels, has 23 cameras and sensors measuring the composition of the rocks and soil. One experiment will see whether it is possible to extract oxygen from the carbon dioxide in the Martian air, while a ground-penetrating radar will look for buried rocks and meteorites, and can detect underground water ice and salty brine at depths of up to 30 ft. “Mars is intricate and complex, and it doesn’t have just one surface,” said Eric Ford, a professor of astrophysics at Penn State. “It’s worthwhile studying Mars.” The 4 lb. helicopter will act as a scout for the rover and is designed to cover 2,000 ft. per day.

Parker Solar Probe

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The Parker Solar Probe will be launched this summer and is designed to fly through the sun's corona. At its closest approach— about 3.8 million from the surface— it will be closer to the Sun than any previous spacecraft. The goal of the mission is to better understand the Sun's magnetic field, the plasma that makes up the corona, and how they interact to form the electrically charged solar wind that streams outward toward the Earth and other planets. For protection, the spacecraft and instruments are housed in a 4.5-inch-thick carbon-composite shield that must bear temperatures as high as 2,500 °F (1,377 °C).

Europa Clipper

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Data from earlier robotic explorers suggest Jupiter's moon Europa has oceans of liquid water under its icy crust. To verify those results and find out if anything might be swimming there, NASA is developing the Europa Clipper. The mission, with a tentative launch set for the mid-2020s, is slated to carry instruments to measure the moon's chemical, thermal, and magnetic anomalies from orbit. A lander (below) has been proposed to directly sample the surface and look for life-supporting molecules.

Ariel

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Astronomers first detected extrasolar planets in 1995, and since then, all we have measured is their masses and orbits. With the European Space Agency's Atmospheric Remote-sensing Infrared Exoplanet Large-survey, or ARIEL, astrophysicists will get spectrographic data on at least 1,000 exoplanets. That will provide answers about the composition of those planets' atmospheres and how they interact with their home stars. Those answers will have to wait, though, since ESA doesn't plan to launch ARIEL until 2028.

BepiColombo

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Mercury is the closest planet to the Sun and also one of the least explored. Robotic flybys have produced images of the planet’s surface, but questions about its chemical composition, core, and thin atmosphere remain unresolved. BepiColombo, a double-probe joint mission of the European Space Agency and the Japan Aerospace Exploration Agency, aims to delve into Mercury’s mysteries, such as its internal composition and the source of its magnetic field. Scientists will also look to answer critical questions of how it fares so close to the Sun.

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Chandrayaan-2

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India, trying to make its name as a spacefaring nation, hopes to launch its first lunar lander by the end of 2018. The Indian Space Research Organisation said Chandrayaan-2’s coordinated orbiter, lander, and 40-lb. rover will collect information on the “lunar topography, mineralogy, elemental abundance, lunar exosphere and signatures of hydroxyl and water-ice.” The moon will soon be crawling with robots: China’s Chang’e 4 rover is also scheduled to land this year, and about a dozen surface missions—including several private ventures—are planned for the next five years. When humans finally return to the moon, it might almost seem crowded.