The first self-driving vehicle on Mars has proven to be a smashing success

火星首辆自动驾驶探测车大获成功

Sometime next week, NASA’s newest rover on Mars, Perseverance, will set a record for the most distance driven by any vehicle on another world. The automobile-sized rover, which landed on Mars in February 2021, will traverse beyond 45.16 km (28.06 miles) across the Martian surface. In doing so it will break the previous distance record held by the long-lived Opportunity rover, which ceased communications with NASA in 2018. 预计在下周的某个时候，NASA 最新的火星探测车“毅力号”（Perseverance）将创下地外行星上车辆行驶距离的最远纪录。这辆汽车大小的探测车于 2021 年 2 月登陆火星，其行驶里程将超过 45.16 公里（28.06 英里）。届时，它将打破由“机遇号”（Opportunity）长期保持的距离纪录，后者已于 2018 年与 NASA 失联。

So how did Perseverance reach this record-setting distance in just a third of the time? A rover that drives itself. 那么，“毅力号”是如何在仅用三分之一的时间内就达到这一纪录里程的呢？答案在于它是一辆能够自动驾驶的探测车。

“The real enabling technology has been its auto navigation system,” said Steven Lee, the project manager for the Perseverance rover at NASA’s Jet Propulsion Laboratory, in an interview. Much like self-driving cars on Earth, Perseverance has sophisticated onboard cameras that image the surrounding terrain, and these images are then processed algorithmically by an onboard computer to calculate the safest route. NASA 喷气推进实验室（JPL）“毅力号”项目经理史蒂文·李（Steven Lee）在接受采访时表示：“真正实现这一突破的技术是它的自动导航系统。”就像地球上的自动驾驶汽车一样，“毅力号”配备了先进的机载摄像头来拍摄周围地形，随后由机载计算机通过算法处理这些图像，从而计算出最安全的行驶路线。

Terrestrial vehicles have some advantages of course, like clearly defined maps, street signs, lanes, and more. Additionally there are plenty of “road” hazards on Mars, from large boulders to sandy slopes. But at least Perseverance does not have to contend with other traffic and bad drivers. 当然，地球上的车辆拥有一些优势，比如清晰的地图、交通标志、车道线等。此外，火星上还有许多“道路”障碍，从巨大的岩石到沙坡应有尽有。但至少，“毅力号”不必应对其他交通工具和糟糕的驾驶员。

The Curiosity rover, largely a twin of Perseverance that launched nine years earlier, had similar imaging capability and algorithms. But its onboard computer was a generation older, and some of its chipset dated back to the 1990s, Lee said. As a result, only about 10 percent of Curiosity’s driving is autonomous because its processing capabilities are too slow. In its decade and a half on Mars, Curiosity has driven 38.6 km. “好奇号”（Curiosity）探测车在九年前发射，它在很大程度上是“毅力号”的孪生兄弟，也具备类似的成像能力和算法。但李指出，它的机载计算机老了一代，部分芯片组甚至可以追溯到 20 世纪 90 年代。因此，“好奇号”只有约 10% 的行驶是自动完成的，因为其处理能力太慢。在火星上服役的 15 年里，“好奇号”总共行驶了 38.6 公里。

By contrast, about 90 percent of the distance driven by Perseverance has been autonomous thanks to its (slightly) more modern Vision Compute Element. This allows the vehicle to perform all of its sensing and computation while its wheels are turning. Not that the vehicle is going super fast, as Perseverance’s maximum wheel speed is about 150 meters per hour. Still, because Perseverance has not had to spend much time stopped to wait for navigation commands from drivers on Earth, the vehicle has been able to maximize the amount of scientific return. 相比之下，“毅力号”约 90% 的行驶里程都是自动完成的，这要归功于它（稍微）更现代化的视觉计算单元。这使得该车能够在车轮转动的同时进行所有的感知和计算。虽然它的速度并不快——最大轮速约为每小时 150 米——但由于“毅力号”不必花费大量时间停下来等待地球驾驶员的导航指令，它得以最大化其科学产出。

A science superstar 科学界的超级明星

“It is very enabling for the science,” said Vivian Sun, the mission’s deputy project scientist. “Not to sell the rover’s other advanced capabilities short, but the driving in particular has allowed us to have a larger scope than previous missions.” “这对科学研究非常有帮助，”该任务的副项目科学家薇薇安·孙（Vivian Sun）说，“并不是说探测车的其他先进功能不重要，但自动驾驶功能确实让我们比以往的任务拥有了更大的探索范围。”

Perseverance’s self-driving ability has nicely complemented its mission. Curiosity landed in Gale Crater and has slowly been making its way up Mount Sharp. It moves less and spends more time systematically taking detailed measurements as it gains altitude. Perseverance, however, landed in Jezero Crater, where its science objectives are more spread out. It has been able to cruise from one location to another, often surprising scientists by turning up at a new site ahead of the planned timeline. “毅力号”的自动驾驶能力与其任务目标形成了良好的互补。“好奇号”降落在盖尔陨石坑（Gale Crater），并一直在缓慢地向夏普山（Mount Sharp）攀登。它移动较少，更多时间花在随着海拔升高而系统地进行详细测量上。然而，“毅力号”降落在耶泽罗陨石坑（Jezero Crater），那里的科学目标分布更为分散。它能够从一个地点巡航到另一个地点，经常提前到达新地点，给科学家们带来惊喜。

And that’s good, because there is a lot of work to do. In Jezero Crater, the rover is studying some of the most ancient rocks in the Solar System, older than any on Earth, dating as far back as about 4 billion years ago. At the time, the planet was in the later stages of the “heavy bombardment” era when rocks were still whizzing around the inner planets in great numbers. But things were starting to settle down. 这很好，因为还有很多工作要做。在耶泽罗陨石坑，探测车正在研究太阳系中最古老的一些岩石，它们比地球上的任何岩石都要古老，可以追溯到约 40 亿年前。当时，火星正处于“后期重轰炸期”的末尾，岩石仍在内行星周围大量穿梭，但情况已开始趋于平稳。

“It’s the first time we’ve been able to investigate this terrain in situ, and that’s been very exciting,” Sun said. During this era, large lakes and possibly even oceans are thought to have existed on Mars. Perseverance is exploring this ancient terrain to better understand what geological and environmental conditions might have existed at the time, and just how conducive the planet might have been to life. Scientists believe the planet might have looked something like the Mojave Desert on Earth, with water flowing through it, but the debate rages on. With Perseverance, there is a lot of data to base it upon. “这是我们第一次能够就地考察这种地形，这非常令人兴奋，”孙说。据推测，在那个时代，火星上可能存在大湖甚至海洋。毅力号正在探索这片古老的地形，以更好地了解当时可能存在的地质和环境条件，以及这颗行星对生命有多大的适宜性。科学家们认为，当时的火星可能看起来像地球上的莫哈韦沙漠，有水流经过，但争论仍在继续。有了“毅力号”，我们有了大量的数据作为研究基础。

Driving on, and on, and on 继续前行，永不停歇

Curiosity is still going strong on Mars after nearly 15 years, and Perseverance operators say the newer rover is doing great as well. After a few years on Mars, Curiosity operators noted significant wear and tear on the vehicle’s wheels. So for Perseverance, the wheels were redesigned, and there are no signs of appreciable wear and tear, Lee said. “好奇号”在火星上服役近 15 年后依然表现强劲，而“毅力号”的操作员表示，这辆较新的探测车表现也同样出色。在火星上运行几年后，“好奇号”的操作员注意到其车轮出现了明显的磨损。因此，李表示，“毅力号”的车轮经过了重新设计，目前没有任何明显的磨损迹象。

The only minor concern at this point is the actuators in the wheels. They were initially life-tested for 20 km of driving, but NASA is in the midst of certifying them to at least 100 km, and possibly longer. Perseverance operates on RTG power and has no propellants, consumables, or lubricants on board. For this reason, Lee said, the vehicle could keep driving itself across Mars for many years to come. 目前唯一的小担忧是车轮中的执行器。它们最初的寿命测试里程为 20 公里，但 NASA 目前正在对其进行认证，以确保其至少能行驶 100 公里，甚至更远。“毅力号”依靠放射性同位素热电机（RTG）供电，机上没有推进剂、消耗品或润滑剂。因此，李表示，这辆车在未来许多年里都可以继续在火星上自动行驶。