by Xinhua writers Yu Fei, Quan Xiaoshu and Li Mi
BEIJING, May 15 (Xinhua) -- A Chinese spacecraft streaked down through the Martian sky on Saturday, becoming the country's first probe to land on a planet other than Earth.
The lander, carrying a Mars rover, touched down at its pre-selected landing area in the southern part of Utopia Planitia, a vast plain on the northern hemisphere of Mars, at 7:18 a.m. (Beijing Time), the China National Space Administration (CNSA) announced.
It took ground controllers more than an hour to establish the success of the pre-programmed landing. They had to wait for the rover to autonomously unfold its solar panels and antenna to send the signals after landing, and there was a time delay of more than 17 minutes due to the 320-million-km distance between Earth and Mars.
"The Mars landing of the Tianwen-1 mission has been a total success," Zhang Kejian, head of the CNSA, announced at the Beijing Aerospace Control Center.
A large screen in the center showed that the probe landed on the Martian surface at 25.1 degrees north latitude and 109.9 degrees east longitude.
After the success was confirmed, space engineers and scientists at the control center hugged each other amid cheers and applause.
Zhang Rongqiao, chief designer of China's first Mars exploration mission, said that the landing had been a textbook case of accuracy. "Today's success is hard-won," he noted.
More than 40 Mars missions have been launched since the 1960s, but only about half have succeeded. The success rate for landing is even lower.
The landing marks an important step in China's interstellar exploration and a leap from the exploration of the Earth-Moon system to interplanetary exploration, said Chinese President Xi Jinping in a congratulatory message.
"The landing left a Chinese mark on Mars for the first time. It is another landmark progress in China's space industry development," said Xi, also general secretary of the Communist Party of China Central Committee and chairman of the Central Military Commission.
It is the first time in the world that orbiting and landing on Mars is completed in one launch mission, and China has come to the forefront of Mars exploration in the world, said Ye Peijian, an academician of the Chinese Academy of Sciences (CAS).
BREATHTAKING LANDING
Tianwen-1, consisting of an orbiter, a lander and a rover, was launched from the Wenchang Spacecraft Launch Site on the coast of southern China's island province of Hainan on July 23, 2020. It was the first step in China's planetary exploration of the solar system, with the aim of completing orbiting, landing and roving on the red planet in one mission.
The name Tianwen, meaning Questions to Heaven, comes from a poem written by the ancient Chinese poet Qu Yuan (circa 340-278 BC). China's first Mars rover is named Zhurong after the god of fire in ancient Chinese mythology, which echoes with the Chinese name of the red planet: Huoxing (the planet of fire).
The spacecraft entered the Mars orbit in February after a journey of nearly seven months through space, and spent about three months surveying potential landing sites.
In the early hours of Saturday, the spacecraft began to descend from its parking orbit, and the entry capsule enclosing the lander and the rover separated from the orbiter at about 4 a.m.
After flying for approximately three hours, the entry capsule hurtled toward the red planet and entered the Mars atmosphere at an altitude of 125 km, initiating the riskiest phase of the whole mission.
First, the specially designed aerodynamic shape of the entry capsule decelerated with the friction of the Martian atmosphere. When the velocity of the spacecraft was lowered from 4.8 km per second to about 460 meters per second, a huge parachute covering an area of about 200 square meters was unfurled to continue reducing the velocity to less than 100 meters per second.
The parachute and the outer shield of the spacecraft were then jettisoned, exposing the lander and rover, and the retrorocket on the lander was fired to further slow the speed of the craft to almost zero.
At about 100 meters above the Martian surface, the craft hovered to identify obstacles and measured the slopes of the surface. Avoiding the obstacles, it selected a relatively flat area and descended slowly, touching down safely with its four buffer legs.
The craft's plummet through the Martian atmosphere, lasting about nine minutes, was extremely complicated with no ground control, and had to be performed by the spacecraft autonomously, said Geng Yan, an official at the Lunar Exploration and Space Program Center of the CNSA.
"Each step had only one chance, and the actions were closely linked. If there had been any flaw, the landing would have failed," said Geng.
After separating from the entry capsule, the orbiter, with a designed lifespan of one Martian year (about 687 days on Earth), was lifted to return to its parking orbit and helped relay communications between the landing vehicle and Earth.
EXPLORING RED PLANET
Wu Yanhua, deputy director of the CNSA, said the Mars rover Zhurong is expected to drive to the surface of Mars and make more scientific discoveries.
Geng said it will take a further seven to eight days for the rover to detect the surrounding environment and conduct self checks before moving down from the lander to the Martian surface.
The six-wheeled solar-powered rover, resembling a blue butterfly and with a mass of 240 kg, has an expected lifespan of at least 90 Martian days (about three months on Earth).
China has constructed Asia's largest steerable radio telescope with an antenna 70 meters in diameter in Wuqing District of northern China's Tianjin to receive data from the Mars exploration mission.
"According to the images sent back from the orbiter earlier, we've found a large crater with a diameter of about 620 meters close to the landing area of the probe," said Zhao Shu, a senior engineer at the National Astronomical Observatories under the CAS.
The camera on the orbiter has taken detailed images at a resolution of about 0.7 meters, revealing the pre-selected landing area has complicated terrain with many rocks and more craters than previously expected, said Wang Chuang, one of the designers of the probe from the China Academy of Space Technology.
"But we believe the design of our probe is capable of landing in and exploring the region," said Wang.
Earlier research showed the landing site could be the edge of an ancient ocean or lake in the early history of Mars. Chinese scientists are looking forward to finding more evidence of water ice.
"We selected this location as it has both the conditions for a safe landing and scientific research value. The location has not been investigated by other countries, so the scientific data can be shared with other countries to enrich human beings' understanding of Mars," said Geng.
The Tianwen-1 mission will map the morphology and geological structure of Mars, investigate the surface soil characteristics and water ice distribution, analyze the material composition of the surface, measure the ionosphere and the characteristics of the Martian climate and surface environment, and perceive the physical fields and internal structure of Mars.
The orbiter is equipped with remote-sensing camera, Mars-orbiting subsurface exploration radar, mineralogy spectrometer, magnetometer, ion and neutral particle analyzer, and energetic particle analyzer.
The rover Zhurong carries the terrain camera, multispectral camera, subsurface exploration radar, surface composition detector, magnetic field detector and meteorology monitor.
The exploration of Mars will not only investigate whether there is or was life on Mars but will also help shed light on the history of evolution and the future development trends of Earth, as well as search for potential living space for human beings, said Li Chunlai, deputy chief designer of China's first Mars exploration mission.
China is a latecomer to planetary exploration. Chinese space experts believe that their Mars exploration does not necessarily repeat the paths of other countries.
"We hope the mission will be innovative and help push forward scientific and technological development," said Geng.
China is considering the possibility of collecting and bringing back samples for its next Mars mission, as well as exploring asteroids and the Jovian system.
Extensive international cooperation has been carried out during the Tianwen-1 mission.
China is working with the European Space Agency and Argentina for the mission's measurement and control, and with France and Austria for the calibration of multiple payloads and data analysis. Enditem
(Liu Xin, Yang Lu and Chen Gang also contributed to the story.)
