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If Perseverance Finds Evidence of Life on Mars, How Will We Recognize It?

If all goes in accordance with plan, the arrival of NASA’s Perseverance rover on February 18, 2021, will mark the top of an period in Mars exploration.

The first period started in 1964 when Mariner 4, the primary profitable Mars spacecraft, flew by the planet and despatched again photos of a seemingly barren, cratered, Moonlike world. To a public raised on fanciful tales of Mars as harsh however liveable land, the views got here as a shock. Subsequent missions painted a extra diverse, nuanced portrait of the Martian atmosphere, elevating hopes for the 1976 Viking missions. Two landers dug into the crimson soil and examined it for indicators of life — however they got here up empty. Those outcomes closed out Era One with a disappointing message: Mars is a lifeless planet.

Over the subsequent twenty years, planetary scientists started to understand that the Viking experiments had been naive, primarily based on inadequate data concerning the geology and chemistry of Mars. The second Mars period started in 1996, when NASA’s Mars Global Surveyor entered orbit and the little Sojourner rover started rolling throughout the floor. The aim this time was to develop a deep understanding of the planet’s historical past and evolution, with a watch towards discovering out if life ever took maintain there, even when it died out billions of years in the past. Over time, spacecraft from India and the European Space Agency (ESA), and now China and the United Arab Emirates, joined the trouble.

Perseverance is the end result of Mars exploration, Era Two. For the primary time, a rover will discover the Martian floor not only for native examine, however to gather samples for return to Earth. All the facility of the world’s analysis laboratories will likely be unleashed on them. The outcomes of these research may lastly uncover the long-sought indicators of alien life, or may significantly strengthen the case that Mars was by no means the dwelling planet we hoped it was.

Scientific curiosity, worldwide competitors, and personal explorers like Elon Musk assure that Era Three of Mars exploration will occur. But what that period seems like will rely profoundly on what Perseverance finds because it samples the panorama round Jezero crater on Mars. You can watch the touchdown dwell (with speed-of-light time delay!) through NASA’s on-line livestream beginning at 2:15PM EST on February 18. After landing, at 8PM EST the identical day, the National Geographic Channel will provide a deep take a look at the mission’s backstory in a two-hour documentary, Built For Mars: The Perseverance Rover.

Even if the touchdown unfolds flawlessly, we cannot know the true which means of Perseverance’s journey till later this decade, when NASA and ESA mount a mission to return its 15-centimeter-long pattern tubes to Earth. I spoke with Ken Williford, deputy undertaking scientist on Perseverance, concerning the mission’s objectives, alongside together with his biggest hopes (and fears) about what the intrepid robotic may discover. A frivolously edited model of our dialog follows.


Perseverance superficially resembles its predecessor, NASA’s Curiosity rover, however I do know that appearances are deceiving. What’s basically completely different about this mission?

Great query. The manner we’re transferring the science ahead with Perseverance is that we’re instantly searching for the indicators of historic life and, as such, instantly searching for proof of life past Earth in a manner that is extra critical than any mission since Viking within the mid Nineteen Seventies. Or extra direct is perhaps a greater phrase. That’s not a knock on Curiosity. I actually labored on that mission and liked it; it was very profitable. We’re standing on the shoulders of giants, but additionally taking the subsequent step.

The factor that is so thrilling to me as an astrobiologist is to get the prospect to be a component of a
mission that’s instantly and explicitly tasked with searching for proof of life past Earth. The key distinction between us and Viking is that Viking was searching for indicators of extant life, organisms which are at present alive or lately deceased, whereas we’re doing one thing very completely different, searching for indicators of historic life, very historic life, three to 4 billion years previous.

Its body may resemble that of Curiosity, but the Perseverance rover has a unique scientific soul of its own. (Credit: NASA/JPL-Caltech)

Its physique could resemble that of Curiosity, however the Perseverance rover has a novel scientific soul of its personal. (Credit: NASA/JPL-Caltech)

What can Perseverance do this Curiosity couldn’t? What are its new capabilities?

I’d say the most important factor that units Perseverance and Curiosity aside in phrases of the {hardware} is our sampling system. Mars 2020 [the original name of Perseverance] is the
first step in what can be a marketing campaign of missions required to pick out and gather samples, retailer them on the floor of Mars, after which finally get them again to Earth for examine in Earth-based labs.

That’s referred to as Mars pattern return. It’s an concept that’s been round for fairly a while, and we’re solely now standing on the edge of actually starting that course of in earnest. We have a brand new science devices, as you mentioned, and we will use these devices to decide on the areas in our exploration space, in and round Jezero crater [the Perseverance landing site on Mars], which have the most effective probability to have preserved indicators of historic life. We’re additionally taking a look at planetary evolution: How did Mars kind and evolve as a planetary system? How is it comparable or completely different to the trail that Earth took as a rocky planet?

We’d like to handle these questions from the floor with our devices, however we’ll additionally take samples with a coring drill. That’s one other huge distinction between the 2 missions. Curiosity’s drill generates powder that it takes onboard the rover to devices contained in the rover to investigate proper there on Mars. Our drill as a substitute makes cores of rock concerning the measurement of a bit of classroom chalk, seals them in titanium tubes which are then positioned on the floor of Mars. Eventually, one other mission picks them up and will get them into orbit. Then a 3rd mission grabs them and flies them again to Earth for all that science that occurs later, again within the Earth-based laboratories.

How will you select the distinctive samples that say to you, “Oh, this is something we want to take a closer look at on Earth?”

We get very particular like that, searching for very particular properties of particular person samples. We additionally take a broader view. One of the primary motivating elements is our curiosity is to
construct a various set of samples, a geologically numerous set of samples. The science staff has spent a few years on that. Other scientists have been utilizing information acquired from orbit. Based on these photos and spectra from orbit across the touchdown website, we have constructed geologic interpretations of how that space developed by time. The crater was shaped by a big effect, a river floated into it, stuffed the crater with a lake. There was a delta that shaped, so the lake had an historic shoreline, it had an historic deepest center half of the lake. It had all these little micro-environments.

The space exterior Jezero is one thing we hope to discover finally as effectively, the crater rim
itself, the historical past of that influence. We’d like to grasp the rocks exterior Jezero that had been there earlier than the crater shaped. Those rocks are on the western edge of a a lot, a lot bigger crater referred to as Isidis that we expect may’ve solely shaped very early in Mars’ historical past. We wish to go to all these completely different rock models and gather samples, as a result of they every include an necessary piece of this grand puzzle that we’re making an attempt to place collectively, which is absolutely about Mars’ historical past as a system. Most thrilling to me is that this query, did life ever emerge on Mars, and if that’s the case, how widespread was it?

Are there particular chemical or structural signatures that may inform you which rocks are probably the most promising ones for getting these solutions?

What we search for in particular person samples, particularly once we’re concentrating on indicators of historic life, is lifelike chemical compositions and lifelike shapes, particularly after they happen collectively. We’ll observe shapes with our cameras which are all around the rover. We’ll observe compositions with our spectrometers, of which we’ve many aboard the rover. We’re searching for lifelike chemical components within the rocks — inorganic minerals and natural matter, and if there’s natural matter what kind is perhaps there.

An enormous technological advance within the instrumentation with Perseverance is that this capability to do what we name spatially resolved evaluation. We have mapping devices which, versus measuring the majority chemistry of one thing that is sort of averaged over a bigger space, perhaps a cubic centimeter or a cubic inch for those who like, they’re rastering a beam, within the case of the PIXL and SHERLOC devices. These two devices have a beam that’s concerning the width of a human hair, about 100 microns, and it scans that beam over the world to
get a map of chemical composition.

Engineers install the sample tubes on Perseverance at the Kennedy Space Center on May 21, 2020. (Credit: NASA/JPL-Caltech/KSC)

Engineers putting in the pattern tubes on Perseverance on the Kennedy Space Center on May 21, 2020. (Credit: NASA/JPL-Caltech/KSC)

Would you be capable of see Mars fossils? Is {that a} chance?

Not particular person cells, except the cells are very massive, and we do not count on to see one thing like that. In truth, one of the primary causes to get the samples again to Earth is so we are able to use gentle microscopy and spectroscopy to get greater spatial decision, even all the way down to nanometer-scale decision. With spatial decision like that, we are able to distinguish particular person fossil cells fairly effectively. There are many examples of them on Earth. Some of the oldest sedimentary rocks on Earth have fossil micro organism in them.

What we are able to see on Mars with Perseverance is larger-scale constructions that may be shaped by single-celled organisms, like microbial mats. We completely can see issues at that scale. Those are virtually meta-shapes shaped by these little cells.

Those constructions might be actually ambiguous, although. The controversy over the life-like constructions within the Mars meteorite, Allan Hills 84001, continues to be unresolved 25 years later.

Yeah, completely. We take into consideration the Alan Hills meteorite rather a lot. It launched rather a lot of fascinating science and in some sense was actually accountable for the growth within the discipline
of astrobiology. The funding that paid for PhD work could effectively not have existed had it not been for that. It set into movement the method I simply described, searching for each lifelike shapes and lifelike compositions after they happen collectively. I feel some folks oversimplify the historical past of the meteorite [and the reported claim of fossil life from Mars]. There was much more to that paper, for those who return and take a look at the main points.

I’m going to provide away my age and allow you to know that I used to be at that press convention in 1996.

Really? Nice!

There’s nonetheless a sensitivity amongst scientists who work in astrobiology to deciphering shapes
alone [as indicators of past life] within the absence of compositional data. Humans are incredible pattern-recognizers. We see issues that are not there on a regular basis. I’m looking my window proper now at shapes I can see within the clouds and that kind of factor. So we’ve to be vigilant in opposition to fooling ourselves, however on the identical time, if we utterly shut down our visible sense and say, “Don’t believe what you see,” then we’re actually in danger of lacking huge issues. It’s one of probably the most fascinating challenges we face with Perseverance: How can we be keep open to fascinating issues on Mars with out unduly fooling ourselves?

Let’s get into it, then! What may a really significant mineral or structural relic of historic life seem like?

There are a quantity of minerals that we regularly discover related to indicators of historic life on Earth. Carbonates are a giant one. On Earth, seashells are made of carbonate minerals. We do not anticipate finding massive, complicated animals of the type that kind seashells on Mars, however even the oldest stromatolites [sedimentary structures associated with bacteria] are shaped from carbonate minerals which have later been partially silicified. Porous fossil microbial mats contained carbonate minerals and a few fluids with dissolved silica flowed into them. In some circumstances, the silica precipitated out, changed some of the supplies within the stromatolite, and led to it being preserved in a manner that it in any other case may not have been, as microcrystal and quartz.

Then there are sulfate and sulfide minerals, sulfur-bearing minerals in each the oxidized and the lowered phases. One manner to have a look at it’s, you might boil it all the way down to the chemical components that you simply’re fascinated by. The core listing for astrobiology are the “CHNOPS elements” [carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur] and we take a look at all of the minerals that bear these components. We have carbonates, sulfates, phosphates, and so on. There are many others. Any case the place you will get redox {couples}, so oxidation and discount chemistry reworking one thing like a sulfate right into a sulfide, any chemical response like that’s one thing {that a} microbe could make its dwelling from.

How a lot of Perseverance’s focus is on planetary geology versus astrobiology? And is there a rigidity between the 2 objectives?

Well, geochronology lies within the realm of planetary evolution, understanding what the inside of Mars is made of and the way that is developed over time. But these huge, broad questions are additionally important to astrobiology; all of these processes allow and regulate the habitability of a planet. How did the non-living methods on the planet evolve and alter in a manner that brought about the planet to be liveable, or that brought about that habitability to break down?

Then once more, the most effective samples for geochronology is probably not greatest for preserving indicators of life. A pure dynamic rigidity exists there. The manner I give it some thought, coming extra from the astrobiology facet, is simply as I mentioned: All that stuff is totally important to the indicators of life and understanding their context. It’s all simply huge, stunning science as effectively.

Jezero crater as it may have appeared 3.5 billion years ago, when Mars was warm and wet. (Credit: NASA/JPL-Caltech)

Jezero crater as it could have appeared 3.5 billion years in the past, when Mars was heat and moist. (Credit: NASA/JPL-Caltech)

Tell me extra about Jezero crater, Perseverance’s touchdown website. Why did you select this specific location?

Well, it very clearly was as soon as a crater lake. There’s an historic river channel flowing into it from the northwest. Less apparent, there’s an outflow channel within the northeastern nook of the crater. Then there’s this huge, stunning delta. If you discover a delta on the finish of a river system inside a basin like a crater, it says there was a standing physique of water right here that was met by a flowing physique of water. In this case, a lake is met by a river, and the river is succesful of carrying all that entrained sediment as a result of there’s vitality of stream. Then when it hits the standing water, the vitality drops and the sediment drops out in a giant pile, similar to the place the Mississippi Delta meets the Gulf of Mexico.

So that is Jezero itself, nevertheless it’s zooming out to the broader area round it that actually led us right here within the first place. The crater sits inside a area that gives entry to not solely the earliest interval of Mars’ historical past however a youthful interval the place we’ve the Syrtis volcanic province [when the huge Martian volcanoes erupted]. Jezero is located between Isidis to the northeast of Jezero and the Syrtis volcanic province to the southwest. Materials from that volcano would’ve been interacting and the influence of that volcanism on the Martian atmosphere would have been recorded to some extent within the rocks round Jezero.

Is it attainable to infer how way back Jezero crater was a lake, and the way lengthy that moist interval lasted?

Our greatest estimate thus far for the age of the Isidis influence, which has to have been sooner than the Jezero influence, is about 3.9 billion years in the past. We are usually not concerning the absolute age of Jezero, nevertheless. The estimates vary as previous as 3.8 billion to a superb bit youthful, however we’re fairly assured it is within the interval between three and 4 billion years in the past. Interestingly, that’s the time once we discover the primary proof of life on Earth.

Perseverance is bringing alongside an experimental helicopter referred to as Ingenuity. Will it provide help to find fascinating locations to discover?

Ingenuity has a well-defined mission that it plans to execute over 30 sols [Martian days] with 5 flights of rising complexity. The mission there’s to show that that flying expertise can work on Mars. It can be actually highly effective in enabling future helicopters that might land and be a significant element of the science exploration. We’re all rooting for the staff and may’t wait to see the photographs that end result, nevertheless it’s not a element of our science mission planning.

What makes Jezero crater such a big place to go prospecting for proof of historic Martian life?

Jezero gives clear set of environments and sub-environments, all of the completely different areas inside the historic crater lake. We can very confidently say, if we go there and we do our job and we gather a various set of examples which were very effectively characterised and we convey them again — if we don’t discover any proof of life in there, that tells us one thing fairly vital. This is a clearly liveable atmosphere early in Mars’ historical past. If life had emerged on Mars, it appears very probably that it might’ve left indicators in an atmosphere like Jezero crater.

That’s fairly a robust assertion! If we convey again samples from Jezero crater and discover no indicators of life, what then? Would the subsequent step be to do a deep drilling mission on Mars?

Yeah, I feel a deep drilling mission or, extra broadly, a mission that appears whether or not there are nonetheless liveable environments on Mars right this moment. We imagine, primarily based on what we all know, that
any trendy life must be confined to the subsurface, perhaps the fairly deep subsurface, so deep drilling is perhaps required.

Part of the best way I take a look at that is that it appears we’re on a path towards human exploration of Mars in maybe the not too distant future. This is one thing I’m very enthusiastic about. The thought of seeing a human being on Mars and having that human come again and relay her expertise to the folks of Earth and present the photographs and every thing… Just to be our consultant there and to have the planet seen instantly by human eyes, that’s actually inspiring to me.

Dead or alive? This famous micrograph of Mars meteorite ALH84001 shows structures that resemble fossils, but most scientists regard them as mineral formations. Perseverance seeks less ambiguous evidence. (Credit: NASA/JSC)

Dead or alive? This well-known micrograph of Mars meteorite ALH84001 exhibits constructions that resemble fossils, however most scientists regard them as mineral formations. Perseverance seeks much less ambiguous proof. (Credit: NASA/JSC)

Do we actually want human exploration to reply the query of life on Mars?

There’s rather a lot of connections and implications between human exploration of Mars and any effort to grasp whether or not Mars may at present be inhabited. Those two efforts are
linked, first of all, from the facet of planetary safety. The Mars 2020 staff spent rather a lot of effort and time constructing a system to keep away from contamination of the Martian floor by Earth organisms within the curiosity of preserving Mars as a pristine atmosphere and preserving our capability to search for proof of life on Mars, extant life. When you convey people, it’s very troublesome to fulfill the stringent planetary safety necessities [preventing contamination] which are the topic of worldwide agreements.

Another actually fascinating connection is that we’ve this instrument on our rover referred to as
MOXIE. It’s a sort of experiment referred to as in-situ useful resource utilization, going to an atmosphere and utilizing one thing that is there to be helpful to your exploration. In this case, MOXIE will likely be producing oxygen from Martian CO2. More broadly, for those who land people on Mars, what sources are they going to have the ability to use there? A key useful resource is water, so touchdown the place there is perhaps entry to water for people is a giant factor that they are considering rather a lot about.

In some methods, then, gained’t human astronauts make the seek for life tougher?

Well, the locations the place you discover water are the locations you would be probably discover any life, in order that’s an fascinating connection. I’m simply wanting ahead to seeing the way it all goes. Right now, we’re targeted on the robotics facet and each defending Mars from undue contamination by Earth organisms. Quite critically, and for the primary time, we’re additionally involved with being half of a bigger system enabling future missions to get the samples that we gather again to Earth. We need to do it safely, resembling that there isn’t a contamination of Earth by any Martian materials, in order that the container that holds these samples is opened in a particularly safe atmosphere and assessed for Earth security previous to all the good science will occurs after these samples make their manner out of the safe facility.

It all comes down to the Mars samples that Perseverance will seal into these 15-centimeter-long titantium tubes and set aside for return to Earth. (Credit: NASA/JPL-Caltech)

It all comes all the way down to the Mars samples that Perseverance will seal into these 15-centimeter-long titantium tubes and put aside for return to Earth. (Credit: NASA/JPL-Caltech)

When the Mars samples come again dwelling, how will you consider them? Do you’ve got a rating system, from mildly fascinating to robust proof of Martian life?

Well, truthfully, my thoughts does not go a lot to eager about in that manner! It can be incredible to search out one thing so extremely thrilling that we’re leaping up and down considering that we perhaps have proof of life on Mars. But proper now my thoughts is simply so targeted on the current concern and with constructing a strategic construction for a mission, in order that whether or not or not we ever discover any proof for all times on Mars, we put collectively a completely phenomenal set of samples. It helps, psychologically, to maintain our focus. It’s not about assuming the worst, it is simply saying, “No matter what, we’ll learn a lot from these samples here.”

Understood. But nonetheless, you have to have thought-about what sorts of proof would get you leaping up and down.

Yes, we’re maintaining our eyes peeled for the kinds of issues we search for once we’re exploring the Precambrian rocks on Earth, the place life is confined to stromatolites and issues like that. We’re searching for constructions like that. I can cease and put collectively a situation that claims we discover one thing like what you see in Australia, referred to as the Mickey Mouse-ears stromatolites.

Excuse me, did you say “Mickey Mouse”?

The canonical [non-biological] stromatolite is a layered dome. When you see it eroded off right into a flat, horizontal aircraft, you see a bunch of concentric circles. Many minerals precipitate that manner. But when life is concerned, typically the layers are of completely different thicknesses, they usually can pinch and swell and wrinkle. Branching is one thing that we see in life expressed everywhere. You’ll see two domes rising out of one, just like the ears of Mickey Mouse on his head. The specifics of the form are very troublesome to unattainable to clarify with out biology. It can be thrilling to search out that in a Mars rock.

If you see a Mickey Mouse mineral construction on Mars, what’s the subsequent step as you attempt to nail down, as soon as and for all, the proof of life?

Even on [ancient] Earth, most of what you discover is ambiguous. Next you take a look at the composition, however you discover compositions that even have some complexity to them; perhaps there’s two completely different chemical compositions in alternating layers. Where it might begin to
get actually profoundly thrilling is that if we begin to see natural matter concentrated in sure layers and never in others, and if it is all organized in some kind of wrinkly, layered, dome-shaped construction. These are proof of historic life we are able to observe on Earth right this moment, they usually’re the closest analog to probably the most highly effective observations we may think about making on Mars.

The probabilities of us discovering that needle within the haystack, that is one other matter. It will get again to the significance of bringing samples again dwelling. There are areas on Earth the place you may need Mickey Mouse ears stromatolite over right here however perhaps you by no means see that. But for those who take a pattern that is wherever close to that factor, it will have some [chemical or microscopic] expression of life inside it, though it will not be apparent to you within the discipline. It will not present up for you till you get it again to the lab, do a bunch of cautious pattern preparation, and take it by a quantity of completely different analytical methods.

That’s extra of the situation that I assume I’d say is even optimistically probably.


For extra space news and concepts, comply with me on Twitter: @coreyspowell

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