A 293-million-mile journey of the NASA Perseverance rover (探测器) to Mars: ended successfully on February 18, 2021, with a picture-perfect landing inside the Jezero Crater. The car-sized, six-wheeled rover, nicknamed Percy is the US space agency's biggest and most advanced explorer to date. Its primary mission is to search for signs of ancient microbial (微生物的) life on Mars.
Landing on Mars is extremely tricky. The Red Planet's gravitational pull causes approaching spacecraft to go faster to high speeds, while its thin atmosphere-just 1 percent that of Earth's-does little to help slow it down as it approaches the surface.
The scientists had to reduce Percy's 12,000 mph speed to a safe landing speed of less than five mph-in just six and a half minutes. The target entry angle also had to be a precise 12 degrees-any steeper, and the spacecraft would burn up; any flatter, and it would get lost in space. It is no wonder that the final approach is often referred to as the "seven minutes of terror. "
Upon attaining a manageable speed, Percy briefly flew over the Martian surface to seek out the perfect landing spot. Its complex map-reading system rapidly scanned the area and matched it with maps in its database to find the best location.
The NASA scientists will spend the next two months testing Percy's scientific instruments. Once ready, the rover will begin to carry out its mission.
"Perseverance is the smartest robot ever made, but confirming that microbial life once existed carries an unusually large burden of proof," said Lori Glaze, director of NASA's Planetary Science Division. "While we'll learn a lot with the great instruments we have aboard the rover, it may very well require the far more well-equipped laboratories and delicate instruments back here on Earth to tell us whether our samples (样本) carry evidence that Mars once harbored life. "
