After 11 years at Mars, NASA’s MAVEN spacecraft went out with a whisper

在火星服役11年后，NASA的MAVEN探测器悄然失联

NASA’s MAVEN spacecraft was in excellent shape when it disappeared behind Mars on December 6 of last year. The routine passage, called an occultation, was supposed to last less than an hour, but ground teams didn’t hear from the spacecraft when it was supposed to regain contact with Earth. 去年12月6日，当NASA的MAVEN探测器消失在火星背面时，其状态依然非常良好。这次例行的掩星过程本应持续不到一小时，但当探测器本该恢复与地球的联系时，地面团队却未能收到任何信号。

The loss of communication triggered contingency plans for engineers to try to restore a link with MAVEN, which orbits Mars more than 200 million miles from Earth. To no avail, they listened for faint signals and uplinked commands in the blind. Hopes of saving the mission faded over time, and NASA officials announced Wednesday that they’re giving up on it. 通信中断触发了应急预案，工程师们试图与远在2亿多英里外的MAVEN探测器重新建立连接。然而，他们盲目地监听微弱信号并发送指令，却始终无果。随着时间推移，挽救任务的希望逐渐渺茫，NASA官员于周三宣布放弃该任务。

“NASA has ceased efforts to search for the MAVEN spacecraft and are beginning activities to decommission the mission,” said Mike Moreau, MAVEN’s project manager at NASA’s Goddard Space Flight Center in Maryland. “NASA已停止搜寻MAVEN探测器，并开始执行任务退役工作，”位于马里兰州的NASA戈达德太空飞行中心MAVEN项目经理迈克·莫罗（Mike Moreau）表示。

Loss of signal

信号丢失

It will take some time for engineers to try to unravel what happened to the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, which launched from Earth in 2013 and arrived in orbit around Mars in 2014 to study the interaction between the Martian atmosphere and the solar wind. MAVEN was an unqualified success, lasting 11 years at Mars and far outliving its original prime mission. 工程师们还需要一段时间来查明“火星大气与挥发物演化”（MAVEN）探测器究竟发生了什么。该探测器于2013年从地球发射，2014年进入火星轨道，旨在研究火星大气与太阳风之间的相互作用。MAVEN任务取得了圆满成功，在火星服役了11年，远远超出了其最初的主要任务期限。

But the spacecraft’s sudden failure was a surprise. Many of NASA’s planetary exploration missions operate for decades. With the scant information available, investigators may never determine exactly what went wrong with MAVEN. 但探测器的突然故障令人意外。NASA的许多行星探测任务都能运行数十年。由于现有信息匮乏，调查人员可能永远无法确定MAVEN究竟出了什么问题。

Investigators are combing through data the spacecraft transmitted before Mars blocked the signal, and engineers were able to recover fragments of telemetry from MAVEN after it reemerged from behind the planet. 调查人员正在梳理探测器在被火星遮挡信号前传输的数据，工程师们也在探测器从行星背面重新出现后，成功恢复了部分遥测数据碎片。

“As part of this investigation, the team members at the Jet Propulsion Laboratory were successful in recovering some fragments of telemetry and Doppler shift data from the spacecraft,” Moreau said. “These data were extracted from recorded signals that were recovered during the hours following the loss of signal.” “作为调查的一部分，喷气推进实验室（JPL）的团队成员成功从探测器中恢复了一些遥测和多普勒频移数据碎片，”莫罗说，“这些数据是从信号丢失后几小时内记录的信号中提取出来的。”

Ground controllers didn’t see these faint signals in real time. They were recorded as part of a separate science campaign seeking to gather information about the density and dynamics of the upper Martian atmosphere, which can distort radio signals that pass through it. 地面控制人员并未实时看到这些微弱信号。它们是作为另一项科学活动的一部分被记录下来的，该活动旨在收集有关火星高层大气密度和动力学的信息，因为这些大气层会扭曲穿过其中的无线电信号。

“One of the bits of that we were able to confirm is an inertial rate measurement that told us the spacecraft was spinning at about 2.7 revolutions per minute,” Moreau said. “We also confirmed that that was consistent with a Doppler signature that we saw in the data. That’s faster than the spacecraft is expected to rotate, and that indicates a problem that the spacecraft probably couldn’t recover from.” “我们确认的一点是惯性速率测量结果，它显示探测器当时正以每分钟约2.7转的速度旋转，”莫罗说，“我们还确认这与我们在数据中看到的多普勒特征一致。这比探测器预期的旋转速度要快，表明探测器可能遇到了无法恢复的问题。”

Without the ability to point its solar arrays toward the Sun, the tumbling spacecraft likely drained its batteries within hours. “That was one of the data points that helped us understand that the spacecraft probably reached a power state that was not supportable to continue operations,” Moreau said. “Those are the facts that we know. The anomaly review board is still looking at the root cause of what actually initiated the failure.” 由于无法将太阳能电池阵列对准太阳，翻滚的探测器很可能在几小时内耗尽了电池电量。“这是帮助我们理解探测器可能已进入无法维持运行的电力状态的数据点之一，”莫罗说，“这就是我们所知的事实。异常审查委员会仍在调查导致故障的根本原因。”

MAVEN is orbiting Mars on an oval-shaped, elliptical path taking it as close as 110 miles (180 km) and as far as 2,500 miles (4,000 km) from the planet’s surface. The spacecraft, about the size of a small car, will remain in this orbit for 50 to 100 years before naturally falling into the Martian atmosphere and burning up. MAVEN正沿着椭圆形轨道绕火星运行，距离火星表面最近处为110英里（180公里），最远处为2500英里（4000公里）。这台大小如小型汽车的探测器将在该轨道上停留50到100年，随后自然坠入火星大气层并烧毁。

What is lost?

失去了什么？

There are two answers to this question. MAVEN was built as a research platform to help scientists understand how the atmosphere of Mars has changed over billions of years. Before MAVEN, scientists knew Mars must have been warmer and wetter and that it had a thicker atmosphere in the ancient past. The atmosphere on Mars today is too thin to support liquid water at the surface, and there is now widespread evidence of a network of lakes and rivers that covered Mars billions of years ago. 这个问题有两个答案。MAVEN被建造为一个研究平台，旨在帮助科学家了解火星大气在数十亿年间是如何变化的。在MAVEN之前，科学家们就知道火星在古代一定更温暖、更湿润，且拥有更厚的大气层。如今火星的大气层太稀薄，无法支持地表存在液态水，但现在有广泛的证据表明，数十亿年前火星曾覆盖着湖泊和河流网络。

MAVEN found evidence of the mechanisms that stripped molecules from the upper layers of the atmosphere, a process known as atmospheric escape. The spacecraft’s science instruments monitored how the Martian atmosphere responded to blasts of charged particles emitted by massive eruptions from the Sun. MAVEN发现了大气层上层分子流失机制的证据，这一过程被称为“大气逃逸”。探测器的科学仪器监测了火星大气如何响应太阳大规模爆发所喷射出的带电粒子流。

“One of our most exciting discoveries used 11 years of MAVEN data to observe, for the first time at any planet, an atmospheric escape process called sputtering,” said Shannon Curry, MAVEN’s principal investigator at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder. “This is where charged particles crash into the upper atmosphere and splash out the neutral atmosphere, much like doing a cannonball in a pool. Our team used noble gas isotopes to confirm that this process has been a dominant escape mechanism for billions of years.” “我们最令人兴奋的发现之一是利用11年的MAVEN数据，首次在任何行星上观测到了一种称为‘溅射’（sputtering）的大气逃逸过程，”科罗拉多大学博尔德分校大气与空间物理实验室的MAVEN首席研究员香农·库里（Shannon Curry）说，“这是带电粒子撞击高层大气并将中性大气‘溅’出去的过程，就像在游泳池里跳水一样。我们的团队利用惰性气体同位素证实，这一过程数十亿年来一直是主要的逃逸机制。”

A solar storm in 2024 hit Mars particularly hard. “We saw orders of magnitude more atmospheric escape, and we even captured images of glowing aurora across the planet,” Curry said. 2024年的一场太阳风暴对火星造成了严重影响。“我们观测到大气逃逸量增加了几个数量级，甚至捕捉到了火星上空发光的极光图像，”库里说。

MAVEN’s scientific legacy is secure, but the goodbye isn’t easy for teams working on the project, which scientists first proposed to NASA in 2006. “I think the team has really experienced the loss of a loved one with the end of the mission,” Moreau said. MAVEN的科学遗产已然稳固，但对于自2006年首次向NASA提出该项目的团队来说，告别并不容易。“我认为团队在任务结束时，确实经历了一种失去挚爱的痛苦，”莫罗说。

“At the same time, we are incredibly proud of the science we’ve accomplished over the last decade,” Curry said. “MAVEN was the best observer of atmospheric escape anywhere in the Solar System. We now have a better understanding of atmospheric escape at Mars than at any other planet, including Earth.” “与此同时，我们对过去十年所取得的科学成就感到无比自豪，”库里说，“MAVEN是太阳系中观测大气逃逸的最佳探测器。我们现在对火星大气逃逸的了解，比包括地球在内的任何其他行星都要深入。”