NASA may already have proof life once existed on another planet. Scientists might never get to find out

A leopard-spotted rock that could prove whether life ever existed beyond Earth is sitting in a tube on Mars.

NASA’s Perseverance rover grabbed up the sample, called Sapphire Canyon, from rocky outcrops on the edges of the Neretva Vallis, a valley sculpted by rivers that once flowed into an ancient lake in Jezero Crater more than 3 billion years ago. The rover landed at the dried lakebed in February 2021 for expressly this purpose, hunting for rocks created or modified by water in the past, which would have had the best chance of preserving evidence of life.

Members of the Perseverance science team have said the Sapphire Canyon sample, about the size of a chalk stick, is exactly the type of rock they hoped the rover would discover.

“This is the first time I think we’ve found something that qualifies as a ‘potential biosignature’” on Mars, said Adrian Broz, a member of Perseverance’s science team and a postdoctoral researcher in the Planetary Surface Processes Lab at Purdue University in Indiana. “It’s currently sealed inside of Perseverance rover’s chassis, and it sits there quietly and awaits return to Earth.”

NASA/JPL-Caltech/ASU/MSSS

But the sample might not make it to our planet, at least not anytime soon.

The Mars Sample Return program, a joint venture by NASA and the European Space Agency to ferry the promising cache back to Earth, attracted intense scrutiny for its high price tag and complex design. After sinking billions of dollars into the endeavor, NASA paused and began reassessing the program in 2024 before canceling it entirely — with no clear alternative in sight.

“While Perseverance’s samples remain safely stored on Mars, NASA is exploring a range of potential return options that could offer simpler and more affordable approaches than the original Mars Sample Return plan, including possible commercial or international contributions,” the agency said in a statement shared with CNN in July. NASA’s leaders still haven’t revealed a path forward.

And while the discovery of the Sapphire Canyon sample is building a strong case for the existence of ancient microbial life on Mars, there’s only so much scientists can learn from afar, said Dr. Briony Horgan, professor of Earth, atmospheric and planetary sciences at Purdue University.

The rover, which cost NASA about $2.4 billion to build and launch, doesn’t have the instrument suite to answer such lofty questions by itself on the red planet.

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“We can keep doing these studies and coming up with these hints, but we’re never going to know for sure until we get those samples back,” said Horgan, also a coinvestigator and planner on the Perseverance team. “These samples are our best current chance for really understanding is life abundant and common, or is Earth truly unique?”

Now, it’s possible one of NASA’s biggest competitors in the new space race will be the first to achieve Mars sample retrieval: China is looking to pick up its own souvenir from the red planet in 2031, and it has taken steps to ensure success by designing a mission that’s similar to one it pulled off two years ago. But the rocks returned by the country’s Tianwen-3 mission, expected to launch in 2028, could look very different — and perhaps offer different insights — from Perseverance’s samples, depending on how plans evolve.

NASA/ESA/JPL-Caltech

Scientists consider Sapphire Canyon such a promising find because of its spotted appearance. On Earth, the tiny dots, called reaction fronts or reduction spots, form in soils and sediments due to the presence of microbial activity.

“When there’s organic matter that’s lodged in sediment or soil that’s buried and microbes start to digest some of that organic matter, they form these bleached halos and spots that are quite resemblant to the ones that Perseverance found in this ancient river valley,” said Broz, coauthor of a study about the rock sample published in September 2025.

NASA/JPL-Caltech/MSSS

Perseverance drilled the Sapphire Canyon sample from an arrowhead-shaped rock called Cheyava Falls in July 2024. The mudstones surrounding the rock were also covered in hundreds of thousands of promising reduction spots potentially made by ancient microscopic life.

Still, returning the samples to Earth is the only way to determine whether these distinctive features were formed by the presence of life, or abiotically — through chemical or geological processes that did not require life, Broz said.

It’s a lesson planetary scientists learned from studying the famed Allan Hills 84001 Martian meteorite , uncovered in the Antarctic in 1984 and originally thought to contain the remnants of ancient life. Multiple groups of scientists analyzed samples from the meteorite, discovering that nonbiological, geological processes left behind signatures that could be misinterpreted as organic carbon compounds attributed to life.

“Even when you have all the labs all over the world looking at a rock that has putative evidence of ancient life, it is a really difficult thing to do, and so you want to just be able to apply every technique you can think of in all the best labs,” said Ashwin Vasavada, project scientist for the Curiosity rover at NASA’s Jet Propulsion Laboratory in Pasadena, California.

The rover’s onboard tools can offer some data, but they weren’t designed to do the kind of analysis necessary to make definitive answers because that wasn’t part of the original plan.

“The science instruments had been selected with the assumption that they would be doing reconnaissance for sample selection and providing the geologic context on Mars for samples that were always expected to be returned to Earth,” said Dr. Melissa Rice, a professor of planetary science at Western Washington University who has worked on NASA rover missions for over two decades.

The first entry in NASA’s budget request to Congress for initial studies of a Mars sample return program occurred in the fiscal year 1978, according to Casey Dreier, chief of space policy at The Planetary Society. The request was made on the heels of the agency’s Viking missions to Mars, considered NASA’s first attempt to search for evidence of life on the red planet.

“It tells you how long it has remained this kind of scientific holy grail for Mars,” Dreier said.

NASA/JPL-Caltech/MRO/HIRISE/UA/ICL

A 2003 survey identifying top scientific objectives for future space missions — and several subsequent reports — highlighted retrieving red planet samples as a key priority, which led to Mars Sample Return becoming intertwined with the Perseverance rover’s mission. The two projects were developed hand in hand.

NASA Jet Propulsion Laboratory

The original concept for Mars Sample Return, shared in 2020 , included a succession of multiple missions launching from Earth to Mars: a lander containing a Mars fetch rover to collect the samples and an ascent vehicle to return the samples to Earth by 2031 at the earliest.

The ascent vehicle was intended to shoot out a football-size container holding the samples that would be captured by a separately launched ESA spacecraft orbiting Mars.

Then, the ESA orbiter would head back to Earth, transferring the sample container into yet another vehicle that could deploy from the orbiter and safely land the samples on our planet.

By 2022, the plan shifted : Perseverance would deliver the sample suite to the Mars Ascent Vehicle that would launch on a return journey. The lander would carry two small recovery helicopters, which could grab samples from the rover if Perseverance wasn’t in good enough condition to make the drive to a landing site. This nudged the return date to 2033.

As things progressed, assessments from independent review boards pointed out how unwieldy and complex the retrieval process had become. The program’s budget ballooned to an eye-popping maximum of $11 billion and the estimated return date for the samples pushed to 2040. NASA also faced budget cuts for the 2024 and 2025 fiscal years, and the excessive costs of the mission led to waning political support for the program.

The agency put out a call for cheaper, quicker and less complex proposals and, in January 2025, identified two strategies that relied on commercial partnerships or leaned on previously used Mars landing technology so as to not reinvent the wheel. That assessment came out just weeks before President Donald Trump took office and began the search for a new NASA administrator.

The next sample return update, revealed with NASA’s fiscal year 2026 budget request , was an abrupt blow: “NASA plans to terminate the Mars Sample Return Program given that current architecture options remain unaffordable. It is anticipated that future missions to Mars will return samples for study on Earth.”

The agency’s 2027 budget request didn’t mention the program at all. NASA spent about $2.5 billion on the Mars Sample Return through its cancellation, Dreier said.

However, NASA administrator Jared Isaacman has mentioned that he’s interested in getting Perseverance’s samples delivered to Earth.

“As I’ve said many times, I think retrieving the samples from Mars can lead to the most significant scientific breakthrough in human history,” Isaacman said at a news conference on August 30 after the successful launch of the Nancy Grace Roman Space Telescope . “There’s no question we’re going to go get samples, whether it’s robotic or whether it’s astronauts picking it up will be the question, and certainly the time frame associated with it.”

Speaking at the All-In Summit in September, Isaacman blamed his predecessors for the program’s failures, noting “the prior administration canceled the Mars Sample Return mission that was on track to cost more than an aircraft carrier.”

While the finger-pointing about the fate of the original program appears to continue, no additional details about next steps have emerged.

China’s plan to fetch Mars samples is also complex, though arguably less so than NASA’s original design. Called Tianwen-3, the approach China is using draws on the success of Chang’e-6, a 2024 mission that retrieved the first samples from the moon’s far side.

Tianwen-3 will include two launches: one for a lander, ascent vehicle and helicopter, and another for an orbiter and return vehicle to shuttle the samples to Earth, according to a study published by the mission team in 2025. The lander is equipped with a drill that can reach 2 meters (6.5 feet) beneath the Martian surface, the ideal place to search for signs of past or present life. The helicopter can also gather rock samples.

CNSA/AFP/Getty Images

Mission scientists plan for the lander to operate on Mars’ surface for about 70 days during sample collection, according to Yiliang Li, a core member of Tianwen-3’s science team who is aiding in the selection of landing sites.

The Tianwen-3 team is narrowing down a list of 86 potential landing sites to identify regions where liquid water once existed on Mars, mineral-enriched regions and areas where ancient microbial activity could still be preserved, according to a 2024 study . Jezero Crater does not appear to be on the list.

Ideally, the mission will retrieve two types of samples from ancient lake beds, said Li, a coauthor on both studies.

The team is aiming to find one sample with iron oxides, which might have preserved cell shapes for billions of years, and a second sample that contains thick aquatic clays because they could contain ancient organic molecules created by living organisms, said Li, who is also a professor of astrobiology in the department of Earth and planetary sciences at the University of Hong Kong.

Zengqian Hou, Tianwen-3’s chief scientist and economic geologist of the Chinese Academy of Sciences, announced in September at the International Deep Space Exploration Conference that engineers are currently building a prototype of Tianwen-3 . China also plans to build a planetary protection laboratory to house the samples, Hou said during the announcement.

In recent years, NASA has focused increasingly on America-first messaging to position the US as leading the charge on marking milestones in space, including of beating China at being the first to land humans on Mars. A sample return win for China would certainly undermine that message.

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“American exceptionalism is being challenged in the high ground of space,” NASA Administrator Isaacman said while testifying on the 2027 NASA budget proposal in April. “To win, we cannot establish programs designed to be ‘too big to fail,’ but at the same time ‘too costly to succeed.’ Nor should it be throwing more money at the problem, but rather fixing the problems, concentrating resources on the mission and delivering outcomes.”

Even as it ramps up the “space race” rhetoric in its efforts to return humans to the moon, the agency has made no mention of the fact that China may be the first to retrieve Martian samples — despite NASA already having a leg up with collected samples that just need to hitch a ride to Earth.

“It’s remarkable that the US has advocated its leadership in this area of space exploration and just handed China the win in that one sector of the space race,” Rice said.

Scientists remain hopeful that the Perseverance samples will be returned in some way, Horgan said. The ongoing work of industry partners is part of what’s keeping researchers optimistic.

Lockheed Martin, for example, has worked with NASA on Mars missions and other sample return efforts in the past, which enabled the company to develop a streamlined concept to pick up the abandoned Perseverance samples, said Whitley Poyser, director of Lockheed Martin’s exploration mission area.

The proposal included a fixed-price mission under $3 billion to return 30 of the rover’s samples to Earth no later than 2037. The concept revolved around using a lightweight Mars Ascent Vehicle, a small lander inspired by Lockheed Martin’s involvement in the InSight mission to Mars , and a compact Earth delivery system derived from lessons the company learned by assisting with the OSIRIS-Rex asteroid sample return mission , Poyser said.

The company remains committed to their plan for retrieving samples from Mars and is prepared if the opportunity comes their way, she said.

“The big area from a technical perspective that needs to mature is Mars ascent, especially if we are going to send someone there and send them back,” Poyser said. “We want to know how it’s going to work. All of those technologies are critical and they can be demonstrated through Mars Sample Return.”

Even if the samples don’t contain signs of life, scientists say that knowledge could present intriguing possibilities, including the idea the spots may have been the work of prebiotic chemistry — the soup of elements, metals and organic carbon that could have formed a cell or living entity but didn’t reach its full potential.

And if it turns out that life never existed on Mars, one of our planet’s closest neighbors, then why did it arise on Earth and not a world with similar conditions during the same time frame?

NASA/ESA/JPL-Caltech/GSFC

Martian samples could tell the tale in a way that Earth’s rocks, shaped and lost over time due to erosion and other processes, can’t — and it’s up to the scientific community to share that message, Rice said.

“I think there’s going to be a lot of advocacy for years to come, making sure that the general public is aware of how close we are to answering those big questions,” she said. “The rocks are there, they’re in their tubes, they’re ready. All we got to do is go get them.”

一块带有豹纹斑点的岩石，或许能够证明地球之外是否曾经存在过生命，它目前被保存在火星上的一个试管中。

美国宇航局的“毅力号”火星车从内雷特瓦河谷边缘的岩石露头上采集了名为“蓝宝石峡谷”的样本。内雷特瓦河谷是由河流侵蚀形成的，这些河流在30多亿年前曾流入耶泽罗陨石坑中的一个古老湖泊。2021年2月，“毅力号”火星车专门为此目的降落在干涸的湖床上，寻找过去由水形成或改造的岩石，这些岩石最有可能保存着生命存在的证据。

“毅力号”科学团队的成员表示，蓝宝石峡谷的样本大小与粉笔棒差不多，正是他们希望探测车能够发现的那种岩石。

“我认为这是我们首次在火星上发现符合‘潜在生物特征’定义的物质，”毅力号火星车科学团队成员、印第安纳州普渡大学行星表面过程实验室博士后研究员阿德里安·布罗兹说。“它目前被密封在毅力号火星车的底盘内，静静地待在那里，等待返回地球。”

NASA/JPL-加州理工学院/亚利桑那州立大学/MSSS

但样本可能不会到达我们的星球，至少近期内不会。

美国宇航局（NASA）和欧洲航天局（ESA）联合开展的火星样本返回计划旨在将极具潜力的火星样本带回地球，但由于其高昂的成本和复杂的设计，该计划备受关注。在投入数十亿美元后，NASA于2024年暂停了该计划并开始重新评估，最终在没有任何明确替代方案的情况下彻底取消了该计划。

“虽然‘毅力号’火星车的样本仍安全保存在火星上，但NASA正在探索一系列潜在的返回方案，这些方案可能比最初的火星样本返回计划更简单、更经济，包括可能的商业或国际捐助，”该机构在7月份发给CNN的一份声明中表示。NASA领导层至今仍未透露未来的计划。

普渡大学地球、大气和行星科学教授布里奥尼·霍根博士表示，虽然蓝宝石峡谷样本的发现为火星上存在古代微生物生命提供了强有力的证据，但科学家们从远处能了解到的信息毕竟有限。

这辆火星探测车耗资美国宇航局约 24 亿美元建造和发射，但它自身并没有足够的仪器来回答火星上如此高深的问题。

厌倦了地球？NASA正在招募志愿者参与为期一年的月球和火星模拟实验。

“我们可以继续进行这些研究，得出这些线索，但在拿到样本之前，我们永远无法确定，”霍根说道，他也是“毅力号”火星车团队的合作研究员和规划者。“这些样本是我们目前真正了解生命是否丰富普遍，还是地球真的独一无二的最佳机会。”

如今，NASA在新一轮太空竞赛中最大的竞争对手之一，有可能率先实现火星样本采集：中国计划在2031年从这颗红色星球带回属于自己的“纪念品”，并已采取措施确保成功，其任务设计与两年前成功完成的任务类似。但预计于2028年发射的中国“天问三号”探测器带回的岩石样本，其外观可能与“毅力号”火星车采集的样本截然不同，或许还能提供不同的信息，这取决于计划的最终进展。

NASA/ESA/JPL-加州理工学院

科学家们认为蓝宝石峡谷是一项极具前景的发现，因为它呈现出斑点状的外观。在地球上，这些被称为反应锋或还原斑的微小斑点，是由于微生物活动而在土壤和沉积物中形成的。

“当有机物滞留在被掩埋的沉积物或土壤中，微生物开始消化其中的一些有机物时，就会形成这些漂白的光晕和斑点，这与“毅力号”在这条古老的河谷中发现的非常相似，”布罗兹说道，他是2025年9月发表的一项关于岩石样本的研究的合著者。

NASA/JPL-Caltech/MSSS

2024 年 7 月，“毅力号”火星探测器从一块名为切亚瓦瀑布的箭头状岩石中钻取了蓝宝石峡谷样本。岩石周围的泥岩上也布满了数十万个有希望的还原斑点，这些斑点可能是古代微生物造成的。

布罗兹说，不过，将样本送回地球是确定这些独特特征是由生命存在形成的，还是非生物的（通过不需要生命的化学或地质过程形成的）唯一方法。

这是行星科学家们从研究著名的艾伦山84001火星陨石中汲取的教训。这块陨石于1984年在南极被发现，最初人们认为它含有远古生命的遗迹。多个科学家团队分析了陨石样本，发现非生物的地质过程留下的痕迹可能会被误解为与生命相关的有机碳化合物。

“即使全世界的实验室都在研究一块可能存在古代生命证据的岩石，这仍然是一件非常困难的事情，所以你只想在所有最好的实验室里应用你能想到的所有技术，”美国宇航局喷气推进实验室（位于加利福尼亚州帕萨迪纳）的好奇号火星车项目科学家阿什温·瓦萨瓦达说道。

探测车的车载工具可以提供一些数据，但它们并非设计用来进行得出明确结论所需的分析，因为这不在最初的计划之内。

“选择这些科学仪器时，我们假设它们将用于侦察火星样本，并为预期会带回地球的样本提供火星地质背景，”西华盛顿大学行星科学教授梅丽莎·赖斯博士说道，她参与美国宇航局火星车任务已有二十多年。

据行星协会太空政策主管凯西·德雷尔称，美国宇航局向国会提交的预算申请中，首次列入火星样本返回计划初步研究的款项是在1978财年。该申请紧随美国宇航局的“海盗号”火星探测任务之后，该任务被认为是美国宇航局首次尝试在火星上寻找生命迹象。

德雷尔说：“这说明火星探测作为科学界的圣杯，已经有多久的历史了。”

NASA/JPL-加州理工学院/MRO/HIRISE/UA/ICL

2003年的一项调查确定了未来太空任务的首要科学目标，随后的多份报告也强调，获取火星样本是重中之重，这使得火星样本返回计划与“毅力号”火星车的任务紧密结合。这两个项目是同步开发的。

美国宇航局喷气推进实验室

2020 年提出的火星样本返回计划最初设想从地球发射多个任务到火星：一个着陆器，其中包含一辆火星取样车，用于收集样本；以及一个上升飞行器，用于最早在 2031 年将样本返回地球。

上升飞行器的目的是发射一个足球大小的容器，容器内装有样本，这些样本将由单独发射的绕火星运行的欧洲航天局航天器捕获。

然后，欧洲航天局的轨道飞行器将返回地球，把样本容器转移到另一个可以从轨道飞行器上展开并安全将样本降落到地球上的飞行器中。

到2022年，计划有所调整：毅力号火星车将把样本套件运送到火星上升飞行器，该飞行器将执行返回任务。着陆器将携带两架小型回收直升机，如果毅力号火星车状况不佳，无法自行抵达着陆点，回收直升机可以从火星车上取回样本。这使得返回日期推迟到了2033年。

随着项目推进，独立审查委员会的评估指出，样本回收过程变得极其繁琐复杂。该项目的预算飙升至惊人的110亿美元，样本的预计返回日期也被推迟到2040年。此外，NASA还面临着2024和2025财年的预算削减，而任务的超高成本也导致该项目在政治上的支持度下降。

该机构公开征集更经济、更快捷、更简便的方案，并在2025年1月确定了两项战略：一项依靠商业合作，另一项则借鉴以往的火星着陆技术，以避免重复发明轮子。这份评估报告发布于唐纳德·特朗普总统就职并开始寻找新任NASA局长前几周。

在NASA 2026财年预算申请中公布的下一个火星样本返回计划更新消息令人震惊：“鉴于目前的方案仍然难以负担，NASA计划终止火星样本返回计划。预计未来的火星任务将带回样本供地球研究。”

德雷尔表示，NASA 2027 年的预算申请中完全没有提及该项目。他指出，NASA 在火星样本返回计划取消前已为此花费了约 25 亿美元。

不过，美国宇航局局长贾里德·艾萨克曼曾表示，他有兴趣将“毅力号”火星车的样本运送到地球。

“正如我多次说过的那样，我认为从火星采集样本可能会带来人类历史上最重大的科学突破，”艾萨克曼在8月30日南希·格雷斯·罗曼太空望远镜成功发射后的新闻发布会上说。“毫无疑问，我们一定会去采集样本，至于是由机器人还是宇航员去采集，以及相关的时间安排，都将是问题所在。”

艾萨克曼在 9 月份的“全力以赴峰会”上发表讲话时，将该计划的失败归咎于他的前任，并指出“前任政府取消了火星样本返回任务，该任务的成本预计将超过一艘航空母舰”。

尽管各方仍在互相指责原计划的命运，但关于下一步措施的更多细节尚未公布。

中国的火星采样计划同样复杂，但或许比NASA最初的设计要简单一些。该计划名为“天问三号”，借鉴了嫦娥六号的成功经验。嫦娥六号于2024年发射，从月球背面采集了首批火星样本。

根据任务团队2025年发布的一份研究报告，天问三号任务将进行两次发射：一次发射着陆器、上升器和直升机，另一次发射轨道器和返回器，将样本送回地球。着陆器配备的钻头可以钻至火星表面以下2米（6.5英尺）处，这是寻找过去或现在生命迹象的理想区域。直升机也可以采集岩石样本。

CNSA/AFP/Getty Images

据天问三号科学团队核心成员李义亮（他正在协助选择着陆点）介绍，任务科学家计划让着陆器在火星表面运行约 70 天以采集样本。

根据2024年的一项研究，天问三号团队正在筛选86个潜在着陆点，以确定火星上曾经存在液态水的区域、富含矿物质的区域以及可能保存有古代微生物活动的区域。杰泽罗陨石坑似乎不在名单之列。

李是这两项研究的合著者，他表示，理想情况下，此次任务将从古代湖床中提取两种类型的样本。

李教授说，该团队的目标是找到一个含有氧化铁的样本，氧化铁可能保存了数十亿年的细胞形状；另一个含有厚厚的水生粘土的样本，因为水生粘土可能含有生物体产生的古代有机分子。李教授同时也是香港大学地球及行星科学系的天体生物学教授。

中国科学院经济地质学家、天问三号首席科学家侯增谦在9月举行的国际深空探测大会上宣布，工程师们目前正在建造天问三号的样机。侯增谦在宣布这一消息时还表示，中国计划建造一座行星保护实验室来存放样本。

近年来，NASA越来越注重“美国优先”的宣传策略，力图将美国塑造成太空探索领域（包括率先将人类送上火星）的领军者，力图超越中国。如果中国在火星探测任务中胜出，无疑会削弱NASA的这一宣传策略。

我们对中国的登月计划了解多少？美国为何如此担忧？

“美国例外论在太空领域正受到挑战，”美国国家航空航天局（NASA）局长艾萨克曼在4月份就2027财年NASA预算提案作证时表示。“为了取得胜利，我们不能设立‘大到不能倒’但同时又‘成本太高而难以成功’的项目。我们也不应该一味地投入更多资金，而应该着眼于解决问题，将资源集中于任务本身，并取得预期成果。”

尽管美国宇航局为了重返月球而加大了“太空竞赛”的宣传力度，但它却只字未提中国可能是第一个取回火星样本的国家——尽管美国宇航局已经收集了一些样本，只需要搭便车就能回到地球，从而占据了优势。

“美国一直标榜自己在太空探索领域处于领先地位，却在太空竞赛的这一领域拱手让给了中国，这真是令人匪夷所思，”赖斯说。

霍根表示，科学家们仍然希望“毅力号”火星车的样本能够以某种方式返回地球。工业合作伙伴的持续努力也是研究人员保持乐观的原因之一。

例如，洛克希德·马丁公司过去曾与美国宇航局合作开展火星任务和其他样本返回工作，这使得该公司能够开发出一种简化的概念来回收被遗弃的“毅力号”火星车的样本，洛克希德·马丁公司探索任务领域主管惠特利·波伊瑟表示。

该提案包括一项价格低于 30 亿美元的固定价格任务，旨在最迟于 2037 年将火星车采集的 30 个样本送回地球。波伊瑟表示，该方案的核心是使用轻型火星上升飞行器、受洛克希德·马丁公司参与“洞察号”火星探测任务启发的小型着陆器，以及从该公司协助“奥西里斯-雷克斯”小行星样本返回任务中汲取的经验教训中发展而来的紧凑型地球传送系统。

她表示，公司仍然致力于从火星采集样本的计划，并已做好准备，一旦机会来临，他们将立即行动。

“从技术角度来看，最需要完善的领域是火星上升技术，特别是如果我们要将宇航员送上火星并安全返回的话，”波伊瑟说。“我们想知道它是如何运作的。所有这些技术都至关重要，而火星样本返回任务可以验证这些技术的有效性。”

即使样本中没有发现生命迹象，科学家也表示，这一发现可能会带来一些有趣的可能性，例如这些斑点可能是生命起源前化学作用的产物——元素、金属和有机碳的混合物可能形成细胞或生命体，但并未充分发挥其潜力。

如果事实证明，火星（我们星球最近的邻居之一）上从未存在过生命，那么为什么生命会在同一时期出现在地球上，而不是出现在其他条件相似的星球上呢？

NASA/ESA/JPL-Caltech/GSFC

赖斯说，火星样本能够以地球岩石无法做到的方式讲述故事——地球岩石由于侵蚀和其他过程，随着时间的推移而形成和消失——而分享这一信息是科学界的责任。

“我认为未来几年将会有很多宣传工作要做，确保公众意识到我们距离解答那些重大问题已经非常接近了，”她说。“石头就在那里，它们被装在管子里，它们已经准备好了。我们所要做的就是去把它们取回来。”