The search for life has led astronomers to the icy moons in our Solar System. Among those moons, Europa has attracted a lot of attention. Europa is Jupiter’s fourth-largest moon—and the sixth-largest in the Solar System—at 3,100 kilometres (1,900 mi) in diameter. Scientists think that its oceans could contain two or three times as much water as Earth’s oceans. The only problem is, that water is hidden under a sheet of planet-wide ice that could be between 2km and 30km (1.2 miles and 18.6 miles) thick.
A team of scientists is working hard on the problem. Andrew Dombard, associate professor of Earth and Environmental Sciences at the University of Illinois at Chicago, is part of a team that presented a possible solution. At the American Geophysical Union meeting in Washington, D.C., they presented their idea: a nuclear-powered tunneling robot that could tunnel its way through the ice and into the ocean.
Scientists with the Deep Carbon Observatory (DCO) are transforming our understanding of life deep inside the Earth, and maybe on other worlds. Their discoveries suggest that abundant life could exist in the sub-surface of other planets and moons, even where temperatures are extreme, and energy and nutrients are scarce. They’ve also discovered that all of the life hidden in the deep Earth contains hundreds of times more carbon than all of humanity, and that the deep biosphere is almost twice the volume of all Earth’s oceans.
“Existing models of the carbon cycle … are still a work in progress.” – Dr. Mark Lever, DCO Deep Life Community Steering Committee.”
The DCO is not a facility, but a group of over 1,000 scientist from 52 countries, including geologists, chemists, physicists, and biologists. They’re nearing the end of a 10-year project to investigate how the Deep Carbon Cycle affects Earth. 90 % of Earth’s carbon is inside the planet, and the DCO is our first effort to really understand it.
The discovery of alien life is one of those things that everyone thinks about at some point. Hollywood has made their version of first contact very clear: huge alien vessels appear over Earth’s cities, panic ensues, and Will Smith saves the day with a Windows 3.1 virus. It’s lots of fun—and who knows?—it may end up being accurate. (Not the Windows 3.1 part.) But sci-fi books and movies aside, what do we really know about our attitude to the discovery of alien life?
We have an organization (SETI) dedicated to detecting the presence of alien civilizations, and we have a prominent scientist (Stephen Hawking) warning against advertising our own presence. Those represent the extremes—actively seeking out alien life vs. hiding from it—but what is the collective attitude towards the discovery of alien life? Scientists at Arizona State University (ASU) have studied that issue and detailed their results in a new study published in the journal Frontiers of Psychology.
The team of scientists tried to gauge people’s reactions to the discovery of alien life in three separate parts of their study. In the first case, they examined media reports of past announcements about the discovery of alien life, for example the announcement in 1996 that evidence of microbial life had been found in a Martian metorite.
Secondly, they asked a sample of over 500 people what their own reactions, and the reactions of the rest of humanity, would be to the hypothetical announcement of alien life.
Thirdly, the 500 people were split into two groups. Half were asked to read and respond to a real newspaper story announcing the discovery of fossilized Martian microbial life. The other half were asked to read and respond to a newspaper article announcing the creation of synthetic life by Craig Venter.
In all three cases the life was microbial in nature. Microbial life is the simplest life form, so it should be what we expect to find. This is certainly true in our own Solar System, since the existence of any other intelligent life has been ruled out here, while microbial life has not.
Also, in all three cases, the language of the respondents and the language in the media reports was analyzed for positive and negative words. A specialized piece of software called Linguistic Inquiry and Word Count (LIWC) was used. It’s text-analysis software that scans written language and identifies instances of words that reflect positive affect, negative affect, reward, or risk. (You can try LIWC here for fun, if you like.)
Analyzing Media Reports
The media reports used in the study were all from what the team considers reputable journalism outlets like The New York Times and Science Magazine. The reports were about things like unidentified signals from space that could have been alien in nature, fossilized microbial remains in meteorites, and the discovery of exoplanets in the habitable zones of other solar systems. There were 15 articles in total.
Overall, the study showed that language in media reports about alien life was more positive than negative, and emphasized reward rather than risk. So people generally find the potential of alien life to be a positive thing and something to be looked forward to. However, this part of the study showed something else: People were more positively disposed towards news of alien life that was microbial than they were towards alien life that could be present on exoplanets, where, presumably, it might be more than merely microbial. So, microbes we can handle, but something more advanced and a little doubt starts to creep in.
Reactions to Hypothetical Announcements of Alien Life
This part of the study aimed to assess people’s beliefs regarding how both they as individuals—and humanity as a whole—might react to the discovery of alien microbial life. The same LIWC software was used to analyze the written responses of the 500 people in the sample group.
The results were similar to the first part of the study, at least for the individuals themselves. Positive affect was more predominant than negative aspect, and words reflecting reward were more predominant than words reflecting risk. This probably isn’t surprising, but the study did show something more interesting.
When participants were asked about how the rest of humanity would respond to the announcement of alien life, the response was different. While positive language still outweighed negative language, and reward still outweighed risk, the differences weren’t as pronounced as they were for individuals. So people seem to think that others won’t be looking forward to the discovery of alien life as much as they themselves do.
Actual Reactions to the Discovery of Extraterrestrial Life
This is hard to measure since we haven’t actually discovered any yet. But there have been times when we thought we might have.
In this part of the study, the group of 500 respondents was split into two groups of 250. The first was asked to read an actual 1996 New York Times article announcing the discovery of fossilized microbes in the Martian meteorite. The second group was asked to read a New York Times article from 2010 announcing the creation of life by Craig Venter. The goal was to find out if the positive bias towards the discovery of microbial life was specific to microbial life, or to scientific advancements overall.
This part of the study found the same emphasis on positive affect over negative affect, and reward over risk. This held true in both cases: the Martian microbial life article, and the artificially created life article. The type of article played a minor role in people’s responses. Results were slightly more positive towards the Martian life story than the artificial life story.
Overall, this study shows that people seem positively disposed towards the discovery of alien life. This is reflected in media coverage, people’s personal responses, and people’s expectations of how others would react.
This is really just the tip of the iceberg, though. As the authors say in their study, this is the first empirical attempt to understand any of this. And the study was only 500 people, all Americans.
How different the results might be in other countries and cultures is still an open question. Would populations whose attitudes are more strongly shaped by religion respond differently? Would the populations of countries that have been invaded and dominated by other countries be more nervous about alien life or habitable exoplanets? There’s only conjecture at this point.
Maybe we’re novelty-seekers and we thrive on new discoveries. Or maybe we’re truth-seekers, and that’s reflected in the study. Maybe some of the positivity reflects our fear of being alone. If Earth is the only life-supporting world, that’s a very lonely proposition. Not only that, but it’s an awesome responsibility: we better not screw it up!
Still, the results are encouraging for humanity. We seem, at least according to this first study, open to the discovery of alien life.
But that might change when the first alien ship casts its shadow over Los Angeles.
When we finally find life somewhere out there beyond Earth, it’ll be at the end of a long search. Life probably won’t announce its presence to us, we’ll have to follow a long chain of clues to find it. Like scientists keep telling us, at the start of that chain of clues is water.
The discovery of the TRAPPIST-1 system last year generated a lot of excitement. 7 planets orbiting the star TRAPPIST-1, only 40 light years from Earth. At the time, astronomers thought at least some of them were Earth-like. But now a new study shows that some of the planets could hold more water than Earth. About 250 times more.
This new study focuses on the density of the 7 TRAPPIST-1 planets. Trying to determine that density is a challenging task, and it involved some of the powerhouses in the world of telescopes. The Spitzer Space Telescope, the Kepler Space Telescope, and the SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) facility at ESO’s Paranal Observatory were all used in the study.
In this study, the observations from the three telescopes were subjected to complex computer modelling to determine the densities of the 7 TRAPPIST planets. As a result, we now know that they are all mostly made of rock, and that some of them could be 5% water by mass. (Earth is only about 0.02% water by mass.)
Finding the densities of these planets was not easy. To do so, scientists had to determine both the mass and the size. The TRAPPIST-1 planets were found using the transit method, where the light of the host star dips as the planets pass between their star and us. The transit method gives us a pretty good idea of the size of the planets, but that’s it.
It’s a lot harder to find the mass, because planets with different masses can have the same orbits and we can’t tell them apart. But in multi-planet systems like TRAPPIST-1, there is a way.
As the planets orbit the TRAPPIST-1 star, more massive planets disturb the orbits of the other planets more than lighter ones. This changes the timing of the transits. These effects are “complicated and very subtle” according to the team, and it took a lot of observation and measurement of the transit timing—and very complex computer modelling—to determine their densities.
Lead author Simon Grimm explains how it was done: “The TRAPPIST-1 planets are so close together that they interfere with each other gravitationally, so the times when they pass in front of the star shift slightly. These shifts depend on the planets’ masses, their distances and other orbital parameters. With a computer model, we simulate the planets’ orbits until the calculated transits agree with the observed values, and hence derive the planetary masses.”
So, what about the water?
First of all, this study didn’t detect water. It detected volatile material which is probably water.
Whether or not they’ve confirmed the presence of water, these are still very important results. We’re getting good at finding exoplanets, and the next step is to determine the properties of any atmospheres that exoplanets have.
Team member Eric Agol comments on the significance: “A goal of exoplanet studies for some time has been to probe the composition of planets that are Earth-like in size and temperature. The discovery of TRAPPIST-1 and the capabilities of ESO’s facilities in Chile and the NASA Spitzer Space Telescope in orbit have made this possible — giving us our first glimpse of what Earth-sized exoplanets are made of!”
This study doesn’t tell us if any of the TRAPPIST planets have life on them, or even if they’re habitable. It’s just one more step on the path to hopefully, maybe, one day, finding life somewhere. Study co-author Brice-Olivier Demory, at the University of Bern, said as much: “Densities, while important clues to the planets’ compositions, do not say anything about habitability. However, our study is an important step forward as we continue to explore whether these planets could support life.”
This is what the study determined about the different planets in the TRAPPIST system:
TRAPPIST 1-b and 1c are the two innermost planets and are likely to have rocky cores and be surrounded by atmospheres much thicker than Earth’s.
TRAPPIST-1d is the lightest of the planets at about 30 percent the mass of Earth. We’re uncertain whether it has a large atmosphere, an ocean or an ice layer.
TRAPPIST-1e is a bit of a surprise. It’s the only planet in the system slightly denser than Earth. It may have a denser iron core, and it does not necessarily have a thick atmosphere, ocean or ice layer. TRAPPIST-1e is a mystery because it appears to be so much rockier than the rest of the planets. It’s the most similar to Earth, in size, density and the amount of radiation it receives from its star.
TRAPPIST-1f, g and h might have frozen surfaces. If they have thin atmospheres, they would be unlikely to contain the heavy molecules that we find on Earth, such as carbon dioxide.
The TRAPPIST-1 system is going to be studied for a very long time. It promises to be one of the first targets for the James Webb Space Telescope (we hope.) It’s a very intriguing system, and whether or not any of the planets are deemed habitable, studying them will teach us a lot about our search for water, habitability, and life.
Researchers at Canada’s McGill University have shown for the first time how existing technology could be used to directly detect life on Mars and other planets. The team conducted tests in Canada’s high arctic, which is a close analog to Martian conditions. They showed how low-weight, low-cost, low-energy instruments could detect and sequence alien micro-organisms. They presented their results in the journal Frontiers in Microbiology.
Getting samples back to a lab to test is a time consuming process here on Earth. Add in the difficulty of returning samples from Mars, or from Ganymede or other worlds in our Solar System, and the search for life looks like a daunting task. But the search for life elsewhere in our Solar System is a major goal of today’s space science. The team at McGill wanted to show that, conceptually at least, samples could be tested, sequenced, and grown in-situ at Mars or other locations. And it looks like they’ve succeeded.
Recent and current missions to Mars have studied the suitability of Mars for life. But they don’t have the ability to look for life itself. The last time a Mars mission was designed to directly search for life was in the 1970’s, when NASA’s Viking 1 and 2 missions landed on the surface. No life was detected, but decades later people still debate the results of those missions.
But Mars is heating up, figuratively speaking, and the sophistication of missions to Mars keeps growing. With crewed missions to Mars a likely reality in the not-too-distant future, the team at McGill is looking ahead to develop tools to search for life there. And they focused on miniature, economical, low-energy technology. Much of the current technology is too large or demanding to be useful on missions to Mars, or to places like Enceladus or Europa, both future destinations in the Search for Life.
“To date, these instruments remain high mass, large in size, and have high energy requirements. Such instruments are entirely unsuited for missions to locations such as Europa or Enceladus for which lander packages are likely to be tightly constrained.”
The team of researchers from McGill, which includes Professor Lyle Whyte and Dr. Jacqueline Goordial, have developed what they are calling the ‘Life Detection Platform (LDP).’ The platform is modular, so that different instruments can be swapped out depending on mission requirements, or as better instruments are developed. As it stands, the Life Detection Platform can culture microorganisms from soil samples, assess microbial activity, and sequence DNA and RNA.
There are already instruments available that can do what the LDP can do, but they’re bulky and require more energy to operate. They aren’t suitable for missions to far-flung destinations like Enceladus or Europa, where sub-surface oceans might harbour life. As the authors say in their study, “To date, these instruments remain high mass, large in size, and have high energy requirements. Such instruments are entirely unsuited for missions to locations such as Europa or Enceladus for which lander packages are likely to be tightly constrained.”
A key part of the system is a miniaturized, portable DNA sequencer called the Oxford Nanopore MiniON. The team of researchers behind this study were able to show for the first time that the MiniON can examine samples in extreme and remote environments. They also showed that when combined with other instruments it can detect active microbial life. The researches succeeded in isolatinh microbial extremophiles, detecting microbial activity, and sequencing the DNA. Very impressive indeed.
These are early days for the Life Detection Platform. The system required hands-on operation in these tests. But it does show proof of concept, an important stage in any technological development. “Humans were required to carry out much of the experimentation in this study, while life detection missions on other planets will need to be robotic,” says Dr Goordial.
“Humans were required to carry out much of the experimentation in this study, while life detection missions on other planets will need to be robotic.” – Dr. J. Goordial
The system as it stands now is useful here on Earth. The same things that allow it to search for and sequence microorganisms on other worlds make it suitable for the same task here on Earth. “The types of analyses performed by our platform are typically carried out in the laboratory, after shipping samples back from the field,” says Dr. Goordial. This makes the system desirable for studying epidemics in remote areas, or in rapidly changing conditions where transporting samples to distant labs can be problematic.
These are very exciting times in the Search for Life in our Solar System. If, or when, we discover microbial life on Mars, Europa, Enceladus, or some other world, it will likely be done robotically, using equipment similar to the LDP.
The only thing cooler than sending a helicopter drone to explore Titan is sending a nuclear powered one to do the job. Called the “Dragonfly” spacecraft, this helicopter drone mission has been selected as one of two finalists for NASA’s robotic exploration missions planned for the mid 2020’s. NASA selected the Dragonfly mission from 12 proposals they were considering under their New Horizons program.
Titan is Saturn’s largest moon, and is a primary target in the search for life in our Solar System. Titan has liquid hydrocarbon lakes on its surface, a carbon-rich chemistry, and sub-surface oceans. Titan also cycles methane the way Earth cycles water.
Dragonfly would fulfill its mission by hopping around on the surface of Titan. Once an initial landing site is selected on Titan, Dragonfly will land there with the assistance of a ‘chute. Dragonfly will spend periods of time on the ground, where it will charge its batteries with its radioisotope thermoelectric generator. Once charged, it would then fly for hours at time, travelling tens of kilometers during each flight. Titan’s dense atmosphere and low gravity (compared to Earth) allows for this type of mission.
During these individual flights, potential landing sites would be identified for further scientific work. Dragonfly will return to its initial landing site, and only visit other sites once they have been verified as safe.
“Titan is a fascinating ocean world,” said APL’s Elizabeth Turtle, principal investigator for Dragonfly. “It’s the only moon in the solar system with a dense atmosphere, weather, clouds, rain, and liquid lakes and seas—and those liquids are ethane and methane. There’s so much amazing science and discovery to be done on Titan, and the entire Dragonfly team and our partners are thrilled to begin the next phase of concept development.”
The science objectives of the Dragonfly mission center around prebiotic organic chemistry and habitability on Titan. It will likely have four instruments:
Being chosen as a finalist has the team behind Dragonfly excited for the project. “This brings us one step closer to launching a bold and very exciting space exploration mission to Titan,” said APL Director Ralph Semmel. “We are grateful for the opportunity to further develop our New Frontiers proposals and excited about the impact these NASA missions will have for the world.”
Exploring Titan holds a daunting set of challenges. But as we’ve seen in recent years, NASA and its partners have the capability to meet those challenges. The JHAPL team behind Dragonfly also designed and built the New Horizons mission to Pluto and the Kuiper Belt object 2014 MU69. Their track record of success has everyone excited about the Dragonfly mission.
The Dragonfly mission, and the other finalist—the Comet Astrobiology Exploration Sample Return being developed by Cornell University and the Goddard Space Flight Center—will each receive funding through the end of 2018 to work on the concepts. In the Spring of 2019, NASA will select one of them and will fund its continued development.
Dragonfly is part of NASA’s New Frontiers program. New Frontiers missions are planetary science missions with a cap of approximately $850 million. New Frontiers missions include the Juno mission to Jupiter, the Osiris-REx asteroid sample-return missions, and the aforementioned New Horizons mission to Pluto.
If we want to send spacecraft to exoplanets to search for life, we better get good at building submarines.
A new study by Dr. Fergus Simpson, of the Institute of Cosmos Sciences at the University of Barcelona, shows that our assumptions about exo-planets may be wrong. We kind of assume that exoplanets will have land masses, even though we don’t know that. Dr. Simpson’s study suggests that we can expect lots of oceans on the habitable worlds that we might discover. In fact, ocean coverage of 90% may be the norm.
Normally, we give something a probability of occurring—in this case a habitable world with land masses—based on our data. And we’re more confident in our prediction if we have more data. So if we find 10 exoplanets, and 7 of them have significant land masses, we think there’s a 70% chance that future exoplanets will have significant land masses. If we find 100 exoplanets, and 70 of them have significant land masses, then we’re even more confident in our 70% prediction.
But the problem is, even though we’ve discovered lots of exoplanets, we don’t know if they have land masses or not. We kind of assume they will, even though the masses of those planets is lower than we expect. This is where the Bayesian methods used in this study come in. They replace evidence with logic, sort of.
In Bayesian logic, probability is assigned to something based on the state of our knowledge and on reasonable expectations. In this case, is it reasonable to expect that habitable exoplanets will have significant landmasses in the same way that Earth does? Based on our current knowledge, it isn’t a reasonable expectation.
According to Dr. Simpson, the anthropic principle comes into play here. We just assume that Earth is some kind of standard for habitable worlds. But, as the study shows, that may not be the case.
“Based on the Earth’s ocean coverage of 71%, we find substantial evidence supporting the hypothesis that anthropic selection effects are at work.” – Dr. Fergus Simpson.
In fact, Earth may be a very finely balanced planet, where the amount of water is just right for there to be significant land masses. The size of the oceanic basins is in tune with the amount of water that Earth retains over time, which produces the continents that rise above the seas. Is there any reason to assume that other worlds will be as finely balanced?
Dr. Simpson says no, there isn’t. “A scenario in which the Earth holds less water than most other habitable planets would be consistent with results from simulations, and could help explain why some planets have been found to be a bit less dense than we expected.” says Simpson.
Simpson’s statistical model shows that oceans dominate other habitable worlds, with most of them being 90% water by surface area. In fact, Earth is very close to being a water world. The video shows what would happen to Earth’s continents if the amount of water increased. There is only a very narrow window in which Earth can have both large land masses, and large oceans.
Dr. Simpson suggests that the fine balance between land and water on Earth’s surface could be one reason we evolved here. This is based partly on his model, which shows that land masses will have larger deserts the smaller the oceans are. And deserts are not the most hospitable place for life, and neither are they biodiverse. Also, biodiversity on land is about 25 times greater than biodiversity in oceans, at least on Earth.
Simpson says that the fine balance between land mass and ocean coverage on Earth could be an important reason why we are here, and not somewhere else.
“Our understanding of the development of life may be far from complete, but it is not so dire that we must adhere to the conventional approximation that all habitable planets have an equal chance of hosting intelligent life,” Simpson concludes.
NASA has announced the discovery of hydrogen in the plumes on Enceladus. This is huge news, and Cassini scientists have looked forward to this day. What it means is that there is a potential source of energy for microbes in the oceans of Enceladus, and that energy from the Sun is not required to support life.
We’ve known about the plumes on Enceladus for a while now, and Cassini has even flown through those plumes to determine their content. But hydrogen was never discovered until now. What it means is that there is a geochemical source for hydrogen in Enceladus’ ocean, coming from the interaction between warm water and rocks.
“This is the closest we’ve come, so far, to identifying a place with some of the ingredients needed for a habitable environment.” – Thomas Zurbuchen, NASA.
This is a capstone finding, according to NASA. As far as we know, life needs three things to exist: water, energy, and the right chemicals. We know it has the necessary chemicals, we know it has water, and we now know it has a source of energy.
On Earth, hydrothermal vents deep in the ocean floor provide the energy for a web of life reliant on those vents. Bacteria live there, forming the base of a food chain that can include tube worms, shrimp, and other life forms. This discovery points to the possibility that similar communities might exist in the sub-surface ocean of Enceladus.
“This is the closest we’ve come, so far, to identifying a place with some of the ingredients needed for a habitable environment,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington.
Microbes in Enceladus’ ocean could use the hydrogen in a process called methanogenesis. They obtain energy by combining hydrogen with dissolved carbon dioxide in the water. This process produces a methane by-product. Methanogenesis is a bedrock process at the root of life here on Earth.
“Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
Hubble Confirms Plumes On Europa
NASA has also announced that the Hubble Space Telescope has confirmed the presence of plumes on another of our Solar System’s icy moons, Europa.
These plumes were first seen by the Hubble in 2014, but were never seen again. Since repeatability is key in science, those findings were put on the back burner. But in 2016, NASA announced today, Hubble spotted them again, in the same place. This is the same spot that the Galileo probe noticed a thermal hot spot.
We don’t know if Europa has hydrogen in its oceans, but it’s easy to see where this is going. NASA’s excitement is palpable.
NASA’s Europa Clipper mission will visit Europa and determine the thickness of its ice layer, as well as the depth and salinity of its ocean. It will also analyze the atmosphere and the composition of the plumes. Europa Clipper will fill in a lot of gaps in our understanding.
Europa Clipper will be launched around 2022, but a mission to Enceladus will have to wait a little longer. One mission under consideration in NASA’s Discovery program is ELF, Enceladus Life Finder. ELF would fly through Enceladus’ plumes 8 or 10 times, taking more detailed samples of their content.
The discovery of hydrogen in the plumes of Enceladus is huge news any way you look at it. But that discovery begs the question: Are we doing it all wrong? Are we looking for life in the wrong places?
The search for life elsewhere in the Universe, so far, has mostly revolved around exoplanets. And then refining that search to identify exoplanets that are in the habitable zones of their stars. We’re searching for other Earths, basically.
But maybe we should be changing our focus. Maybe it’s the ice worlds, including icy exomoons, that are the most likely targets for our search. This new evidence from NASA’s Cassini mission, and from the Hubble Space Telescope, suggests that in our Solar System at least, they are the best place to search.
One Final Ingredient Needed?
There’s a fourth ingredient needed for life. Once there is water, energy, and the necessary chemicals, life needs time to get going. How much time, we’re not exactly certain. But this is where Enceladus and Europa are different.
Europa is about 4 billion years old, or so we think. That’s only half a billion years younger than Earth, and we think life started on Earth about 3.5 billion years ago. This hints that, if conditions on Europa are favorable, life has had a long time to get going. Of course, that doesn’t mean it has.
On the other hand, Enceladus is probably much younger. A study of the orbits of Saturn’s moons suggests that Enceladus may only be 100 million years old. If that’s true, it’s not very much time for life to get going.
The hydrogen discovery is huge news. There are still a lot of questions, of course, and lots to be debated. But confirming a source of energy on Enceladus builds the case for the same type of hydrothermal vent life that we see on Earth.
For a long time, the idea of finding life on other worlds was just a science fiction dream. But in our modern times, the search for life is rapidly becoming a practical endeavour. Now, some minds at NASA are looking ahead to the search for life on other worlds, and figuring out how to search more effectively and efficiently. Their approach is centered around two things: nano-satellites and microfluidics.
Life is obvious on Earth. But it’s a different story for the other worlds in our Solar System. Mars is our main target right now, with the work that MSL Curiosity is doing. But Curiosity is investigating Mars to find out if conditions on that planet were ever favorable for life. A more exciting possibility is finding extant life on another world: that is, life that exists right now.
At the Planetary Science Vision 2050 Workshop, experts in Planetary Science and related disciplines gathered to present ideas about the next 50 years of exploration in the Solar System. A team led by Richard Quinn at the NASA Ames Research Center (ARC) presented their ideas on the search for extant life in the next few decades.
Quinn and his team outlined two technologies that we could center our search around.
A nanosatellite is classified as something with a mass between 1-10 kg. They offer several advantages over larger designs.
Firstly, their small mass keeps the cost of launching them very low. In many cases, nanosatellites can be piggy-backed onto the launch of a larger payload, just to use up any excess capacity. Nanosatellites can be made cheaply, and multiples of them can be designed and built the same. This would allow a fleet of nanosatellites to be sent to the same destination.
Most of the discussion around the search for life centers around large craft or landers that land in one location, and have limited mobility. The Mars rovers are doing great work, but they can only investigate very specific locations. In a way, this creates kind of a sampling error. It’s difficult to generalize about the conditions for life on other worlds when we’ve only sampled a small handful of locations.
On Earth, life is everywhere. But Earth is also the home to extremophiles, organisms that exist only in extreme, hard-to-reach locations. Think of thermal vents on the ocean floor, or deep dark caves. If that is the kind of life that exists on the target worlds in our Solar System, then there’s a strong possibility that we’ll need to sample many locations before we find them. That is something that is beyond the capabilities of our rovers. Nanosatellites could be part of the solution. A fleet of them investigating a world like Enceladus or Europa could speed up our search for extant life.
NASA has designed and built nanosatellites to perform a variety of tasks, like performing biology experiments, and testing advanced propulsion and communications technologies. In 2010 they successfully deployed a nanosatellite from a larger, microsatellite. If you expand on that idea, you can see how a small fleet of nanosatellites could be deployed at another world, after arriving there on another larger craft.
Microfluidics deals with systems that manipulate very small amounts of fluid, usually on the sub-millimeter scale. The idea is to build microchips which handle very small sample sizes, and test them in-situ. NASA has done work with microfluidics to try to develop ways of monitoring astronauts’ health on long space voyages, where there is no access to a lab. Microfluidic chips can be manufactured which have only one or two functions, and produce only one or two results.
In terms of the search for extant life in our Solar System, microfluidics is a natural fit with nanosatellites. Replace the medical diagnostic capabilities of a microfluidic chip with a biomarker diagnostic, and you have a tiny device that can be mounted on a tiny satellite. Since functioning microfluidic chips can be as small as microprocessors, multiples of them could be mounted.
” Technical constraints will inevitably limit robotic missions that search for evidence of life to a few selected experiments.” – Richard.C.Quinn, et. al.
When combined with nanosatellites, microfluidics offers the possibility of the same few tests for life being repeated over and over in multiple locations. This is obviously very attractive when it comes to the search for life. The team behind the idea stresses that their approach would involve the search for simple building blocks, the complex biomolecules involved in basic biochemistry, and also the structures that cellular life requires in order to exist. Performing these tests in multiple locations would be a boon in the search.
Some of the technologies for the microfluidic search for life have already been developed. The team points out that several of them have already had successful demonstrations in micro-gravity missions like the GeneSat, the PharmaSat, and the SporeSat.
“The combination of microfluidic systems with chemical and biochemical sensors and sensor arrays offer some of the most promising approaches for extant life detection using small-payload platforms.” – Richard.C.Quinn, et. al.
Putting It All Together
We’re a ways away from a mission to Europa or Enceladus. But this paper was about the future vision of the search for extant life. It’s never too soon to start thinking about that.
There are some obvious obstacles to using nanosatellites to search for life on Enceladus or Europa. Those worlds are frozen, and it’s the oceans under those thick ice caps that we need to investigate. Somehow, our tiny nanosatellites would need to get through that ice.
Also, the nanosatellites we have now are just that: satellites. They are designed to be in orbit around a body. How could they be transformed into tiny, ocean-going submersible explorers?
There’s no doubt that somebody, somewhere at NASA, is already thinking about that.
The over-arching vision of a fleet of small craft, each with the ability to repeat basic experiments searching for life in multiple locations, is a sound one. As for how it actually turns out, we’ll have to wait and see.