This artist’s rendering exhibits the Tianwen-2 spacecraft approaching the near-Earth asteroid 469219 Kamo‘oalewa.
Credit score: CCTV
Six centuries in the past, Admiral Zheng He commanded seven “treasure voyages” round Asia within the halcyon days of China’s Ming Dynasty. His fleet of colossal four-masted wood junks — the most important ships of their day, every crewed by lots of of mariners — plied the South China Sea and Indian Ocean, touring so far as Arabia, the Persian Gulf, and East Africa on missions of diplomacy, commerce, and energy projection throughout the identified world.
In an identical vein, trendy China’s projection of its area energy has moved swiftly for the reason that daybreak of the millennium. China turned the third nation after Russia and the U.S. to independently launch a person into area in 2003, earlier than vigorously pursuing a steady off-planet human presence since 2022. The nation additionally has made little secret of its grandiose ambitions for a human habitat on the Moon within the subsequent decade.
China additionally landed robotic rovers on the lunar floor in 2013 and on Mars in 2021. And it scored a pair of empirical firsts: the primary touchdown of a spacecraft on the Moon’s farside in 2019, and the primary return of farside soil samples to Earth final yr.
This summer season, a mission initially named in Zheng He’s honor however now referred to as Tianwen-2 will propel China deeper into area than ever earlier than — its first foray into the asteroid belt. It follows on the heels of Tianwen-1, China’s first Mars mission, launched in 2020.
The mission’s title comes from an historical Chinese language poem of questions addressed to Tian, the legendary personification of the heavens. Tianwen-2 will deal with a number of questions in regards to the start of the photo voltaic system, the origins of water, and the emergence of life.
Over its decade-long voyage in deep area, Tianwen-2 will collect floor specimens from 469219 Kamo‘oalewa, a near-Earth object in an identical orbit to ours, then return them in a pattern capsule for a parachute-assisted touchdown in China’s Gobi Desert in 2027. It’s going to then embark on a seven-year-plus outbound trek to review 311P/PanSTARRS, a curious primordial physique that bears the hallmarks each of an asteroid and a comet.
The spacecraft
Conceived in 2019, Tianwen-2 was initially slated to launch in 2022 however its schedule slid. After a design examine by the Chinese language Academy of Area Expertise, eight science devices have been chosen in October 2019. They embody seen and infrared spectrometers, a thermal radiation spectrometer, cameras, a 4 ft (1.2 m) imaging radar, charged and impartial particle sensors, and a magnetometer.
The Russian Academy of Sciences can also be contributing an instrument to Tianwen-2 and in 2020, Chinese language center faculty and elementary college students have been invited to suggest fashionable science experiments for the mission.
Tianwen-2 will launch atop a Lengthy March 3B/E rocket from the Xichang Satellite tv for pc Launch Middle in south-central China. First utilized in 2007, this rocket’s spectacular pedigree consists of the launches of China’s first Moon lander and rover (Chang’e-3 in 2013) and the primary spacecraft to land on the lunar far aspect (Chang’e-4 in 2018).
After leaving Earth, Tianwen-2 will attain Kamo‘oalewa by July 2026. This tiny, elongated asteroid doubtless spans not more than 130 to 330 ft (40 to 100 meters). It circles the Solar at a imply distance of 0.9 to 1.1 astronomical items (AU: the common Earth-Solar distance) with a sidereal interval of 365.7 days, comparable orbital parameters to Earth itself.
In regards to the asteroid
Found in April 2016 by the Panoramic Survey Telescope and Fast Response System (PanSTARRS) at Haleakala Observatory in Hawaii, it was initially referred to as 2016 HO3, then renamed Kamo‘oalewa in 2019. The title is a local Hawaiian chant for an oscillating fragment — a becoming moniker given the asteroid’s oscillatory jostling movement because it orbits Earth from 38 lunar distances at its closest level to 100 lunar distances at its farthest.
Kamo‘oalewa’s bodily closeness has prompted astronomers to label it a quasi-satellite of Earth. It isn’t gravitationally certain to us just like the Moon, and is just too distant to represent a real pure satellite tv for pc, but this tiny rock has been our planet’s fixed companion for greater than a century and can most likely stay so for a minimum of one other 300 years.
Regardless of its proximity, Kamo‘oalewa’s minuscule dimension renders our information of it a digital clean. It’s too small for radar starting from Earth to ascertain dependable echoes to estimate its dimension or form. We do know that it rotates quickly — each 28 minutes — and it would nicely be a liberated fragment from the Moon.
In April 2024, reconstructions of the affect dynamics that shaped the Moon’s 13.7-mile (22 km) Giordano Bruno crater a number of million years in the past might need ejected particles into area that ultimately achieved a 1:1 orbital resonance with Earth — matching Kamo‘oalewa’s current location and orbital parameters. Certainly, ground-based spectroscopy hints at a lunar (moderately than asteroidal) origin of its floor supplies.
Kamo‘oalewa’s closeness has additionally pushed an elevated urge for food for exploration, spawning a number of mission proposals in recent times utilizing photo voltaic electrical propulsion, or photo voltaic sails. In 2022, it was postulated that the asteroid’s subsurface may afford a radiation-safe habitat for future Mars astronauts, its fast rotation imparting centrifugal forces to make the voyage extra tolerable on the human physique.
At Kamo‘oalewa
When Tianwen-2 arrives at Kamo‘oalewa, it can make use of twin strategies to seize floor samples. The primary, referred to as “touch-and-go,” was utilized by Japan’s Hayabusa-2 spacecraft at asteroid Ryugu in 2018 and by NASA’s OSIRIS-REx at asteroid Bennu in 2020. However Tianwen-2 can even take a look at a way referred to as “anchor-and-attach,” utilizing 4 robotic arms with drills at their tricks to affix itself to the asteroid’s floor. This difficult manouvre calls for beautiful spacecraft steerage, navigation, and management to get shut sufficient for precision sampling. Additional complicating issues are Kamo‘oalewa’s fast rotation and low gravity, requiring vital automation aboard Tianwen-2.
The spacecraft goals to assemble between 0.7 and three.5 ounces (20 to 100 grams) of regolith from Kamo‘oalewa. It’s thought the asteroid’s floor is a rubble-pile mixture with boulders ranging in dimension up to a couple tens of centimeters and finer particles as much as 0.04 inch (1 mm). Tianwen-2 can even measure Kamo‘oalewa’s bulk parameters — orbital parts, rotation fee, mass, form, gravitational area, and thermal properties.
If profitable, it can mark the primary use of the anchor-and-attach sampling structure in deep area. Tianwen-2 will spend as much as a yr in Kamo‘oalewa’s neighborhood, departing in April 2027 for return to Earth. It’s going to launch the pattern capsule in November 2027 to re-enter Earth’s environment at a blistering Mach 35 — 27,000 mph (43,450 km/h), 10 % quicker than Apollo astronauts throughout their fiery return from the Moon.
Onward to a comet
In the meantime, Tianwen-2 will proceed its trek to 311P/PanSTARRS, a main-belt comet additionally referred to as an energetic asteroid: an object that inhabits an asteroid-like orbit however whose visible options carefully mirror a comet. Found by PanSTARRS in August 2013, it measures 1,570 ft (480 m) in diameter — bigger than a metropolis block — and circles the Solar each 3.24 years at a distance starting from 1.94 to 2.44 AU.
A month after its discovery, in September 2013, 311P/PanSTARRS was noticed by the Hubble Area Telescope and unveiled its oddness — exhibiting substantial structural adjustments and 6 comet-like tails. These could characterize ejected materials from episodic mass loss induced by its fast rotation, as mud avalanches alongside its equator then shear away and drift into area in icy tails.
Present plans envisage Tianwen-2 reaching 311P/PanSTARRS in early 2035 for a yr of observations. It’s hoped that research of each Kamo‘oalewa and 311P/PanSTARRS will furnish new insights into the formation and evolution of primordial photo voltaic system our bodies and supply necessary insights into the origins of water and natural life.
The way forward for the Tianwen program carries nice promise. Tianwen-3, focusing on a 2028 launch, will return the primary Mars soil samples to Earth, whereas 2029’s Tianwen-4 will ship an orbiter to Jupiter and its rocky moon, Callisto. And Zheng He, the Fifteenth-century admiral who for a time lent his title to Tianwen-2, would certainly approve of the riches that trendy China’s spacefaring treasure ships will deliver again dwelling.
