Building Rovers That Can Detect Life and Sequence DNA on Other Worlds

In 2015, then-NASA Chief Scientist Ellen Stofan stated that, “I believe we are going to have strong indications of life beyond Earth in the next decade and definite evidence in the next 10 to 20 years.” With multiple missions scheduled to search foe evidence of life (past and present) on Mars and in the outer Solar System, this hardly seems like an unrealistic appraisal.

But of course, finding evidence of life is no easy task. In addition to concerns over contamination, there is also the and the hazards the comes with operating in extreme environments – which looking for life in the Solar System will certainly involve. All of these concerns were raised at a new FISO conference titled “Towards In-Situ Sequencing for Life Detection“, hosted by Christopher Carr of MIT.

Carr is a research scientist with MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS) and a Research Fellow with the Department of Molecular Biology at Massachusetts General Hospital. For almost 20 years, he has dedicated himself to the study of life and the search for it on other planets. Hence why he is also the science principal investigator (PI) of the Search for Extra-Terrestrial Genomes (SETG) instrument.

This artist’s rendering shows NASA’s Europa mission spacecraft, which will search for life on Europa beginning sometime in the 2020s. Credit: NASA/JPL-Caltech

Led by Dr. Maria T. Zuber – the E. A. Griswold Professor of Geophysics at MIT and the head of EAPS – the inter-disciplinary group behind SETG includes researchers and scientists from MIT, Caltech, Brown University, arvard, and Claremont Biosolutions. With support from NASA, the SETG team has been working towards the development of a system that can test for life in-situ.

Introducing the search for extra-terrestrial life, Carr described the basic approach as follows:

“We could look for life as we don’t know it. But I think it’s important to start from life as we know it – to extract both properties of life and features of life, and consider whether we should be looking for life as we know it as well, in the context of searching for life beyond Earth.”

Towards this end, the SETG team seeks to leverage recent developments in in-situ biological testing to create an instrument that can be used by robotic missions. These developments include the creation of portable DNA/RNA testing devices like the MinION, as well as the Biomolecule Sequencer investigation. Performed by astronaut Kate Rubin in 2016, this was first-ever DNA sequencing to take place aboard the International Space Station.

Building on these, and the upcoming Genes in Space program – which will allow ISS crews to sequence and research DNA samples on site – the SETG team is looking to create an instrument that can isolate, detect, and classify any DNA or RNA-based organisms in extra-terrestrial environments. In the process, it will allow scientists to test the hypothesis that life on Mars and other locations in the Solar System (if it exists) is related to life on Earth.

The theory of Lithopanspermia states that life can be shared between planets within a planetary system. Credit: NASA

To break this hypothesis down, it is a widely accepted theory that the synthesis of complex organics – which includes nucleobases and ribose precursors – occurred early in the history of the Solar System and took place within the Solar nebula from which the planets all formed. These organics may have then been delivered by comets and meteorites to multiple potentially-habitable zones during the Late Heavy Bombardment period.

Known as lithopansermia, this theory is a slight twist on the idea that life is distributed throughout the cosmos by comets, asteroids and planetoids (aka. panspermia). In the case of Earth and Mars, evidence that life might be related is based in part on meteorite samples that are known to have come to Earth from the Red Planet. These were themselves the product of asteroids striking Mars and kicking up ejecta that was eventually captured by Earth.

By investigating locations like Mars, Europa and Enceladus, scientists will also be able to engage in a more direct approach when it comes to searching for life. As Carr explained:

“There’s a couple main approaches. We can take an indirect approach, looking at some of the recently identified exoplanets. And the hope is that with the James Webb Space Telescope and other ground-based telescopes and space-based telescopes, that we will be in a position to begin imaging the atmospheres of exoplanets in much greater detail than characterization of those exoplanets has [allowed for] to date. And that will give us high-end, it will give the ability to look at many different potential worlds. But it’s not going to allow us to go there. And we will only have indirect evidence through, for example, atmospheric spectra.”

Enceladus in all its glory. NASA has announced that Enceladus, Saturn’s icy moon, has hydrogen in its oceans. Image: NASA/JPL/Space Science Institute

Mars, Europa and Enceladus present a direct opportunity to find life since all have demonstrated conditions that are (or were) conducive to life. Whereas there is ample evidence that Mars once had liquid water on its surface, Europa and Enceladus both have subsurface oceans and have shown evidence of being geologically active. Hence, any mission to these worlds would be tasked with looking in the right locations to spot evidence of life.

On Mars, Carr notes, this will come down to looking in places there there is a water-cycle, and will likely involve some a little spelunking:

“I think our best bet is to access the subsurface. And this is very hard. We need to drill, or otherwise access regions below the reach of space radiation which could destroy organic materiel. And one possibility is to go to fresh impact craters. These impact craters could expose material that wasn’t radiation-processed. And maybe a region where we might want to go would be somewhere where a fresh impact crater could connect to a deeper subsurface network – where we could get access to material perhaps coming out of the subsurface. I think that is probably our best bet for finding life on Mars today at the moment. And one place we could look would be within caves; for example, a lava tube or some other kind of cave system that could offer UV-radiation shielding and maybe also provide some access to deeper regions within the Martian surface.”

As for “ocean worlds” like Enceladus, looking for signs of life would likely involve exploring around its southern polar region where tall plumes of water have been observed and studied in the past. On Europa, it would likely involve seeking out “chaos regions”, the spots where there may be interactions between the surface ice and the interior ocean.

Exploring Europa’s “chaos terrain”, where the is interaction between the interior ocean and the surface ice, could yield evidence of biological organisms. Credit: NASA/JPL-Caltech

Exploring these environments naturally presents some serious engineering challenges. For starters, it would require the extensive planetary protections to ensure that contamination was prevented. These protections would also be necessary to ensure that false positives were avoided. Nothing worse than discovering a strain of DNA on another astronomical body, only to realize that it was actually a skin flake that fell into the scanner before launch!

And then there are the difficulties posed by operating a robotic mission in an extreme environment. On Mars, there is always the issue of solar radiation and dust storms. But on Europa, there is the added danger posed by Jupiter’s intense magnetic environment. Exploring water plumes coming from Enceladus is also very challenging for an orbiter that would most likely be speeding past the planet at the time.

But given the potential for scientific breakthroughs, such a mission it is well worth the aches and pains. Not only would it allow astronomers to test theories about the evolution and distribution of life in our Solar System, it could also facilitate the development of crucial space exploration technologies, and result in some serious commercial applications.

Looking to the future, advances in synthetic biology are expected to lead to new treatments for diseases and the ability to 3-D print biological tissues (aka. “bioprinting”). It will also help ensure human health in space by addressing bone density loss, muscle atrophy, and diminished organ and immune-function. And then there’s the ability to grow organisms specially-designed for life on other planets (can you say terraforming?)

Exogenesis
Is life in our Solar System, and the Universe for that matter, universal in nature? Credit: NASA/Jenny Mottor

On top of all that, the ability to conduct in-situ searches for life on other Solar planets also presents scientists with the opportunity to answer a burning question, one which they’ve struggled with for decades. In short, is carbon-based life universal? So far, any and all attempts to answer this question have been largely theoretical and have involved the “low hanging fruit variety” – where we have looked for signs of life as we know it, using mainly indirect methods.

By finding examples that come from environments other than Earth, we would be taking some crucial steps towards preparing ourselves for the kinds of “close encounters” that could be happening down the road.

Further Reading: SETG, FISO

TRAPPIST-1 System Ideal For Life Swapping

Back in February of 2017, NASA announced the discovery of a seven-planet system orbiting a nearby star. This system, known as TRAPPIST-1, is of particular interest to astronomers because of the nature and orbits of the planets. Not only are all seven planets terrestrial in nature (i.e. rocky), but three of the seven have been confirmed to be within the star’s habitable zone (aka. “Goldilocks Zone”).

But beyond the chance that some of these planets could be inhabited, there is also the possibility that their proximity to each other could allow for life to be transferred between them. That is the possibility that a team of scientists from the University of Chicago sought to address in a new study. In the end, they concluded that bacteria and single-celled organisms could be hopping from planet to planet.

This study, titled “Fast Litho-panspermia in the Habitable Zone of the TRAPPIST-1 System“, was recently published in the Astrophysical Journal Letters. For the sake of seeing if life could be distributed within this star system (aka. litho-panspermia), Krijt and his fellow UChicago scientists ran simulations that showed that this process could happen 4 to 5 times faster than it would in our Solar System.

This artist’s concept shows what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances. Credits: NASA/JPL-Caltech

As Sebastiaan Krijt – a postdoctoral scholar at UChicago and the lead author on the study – said in a University press release:

“Frequent material exchange between adjacent planets in the tightly packed TRAPPIST-1 system appears likely. If any of those materials contained life, it’s possible they could inoculate another planet with life.”

For the sake of their study, the team considered that any transfers of life would likely involve asteroids or comets striking planets within the star’s habitable zone (HZ) and then transferring the resulting material to other planets. They then simulated the trajectories that the ejecta would take, and tested to see if it would have the necessary speed to get out of orbit (escape velocity) and be captured by a neighboring planet’s gravity.

In the end, they determined that roughly 10% of the material that would be capable of transferring life would have the velocity necessary to not only achieve escape velocity. This covered the pieces of ejecta that would be large enough to endure irradiation and the heat of re-entry. What’s more, they found that this material would be able to reach another HZ planet with periods ranging from 10 to 100 years.

Illustration showing the possible surface of TRAPPIST-1f, one of the newly discovered planets in the TRAPPIST-1 system. Credits: NASA/JPL-Caltech
Illustration showing the possible surface of TRAPPIST-1f, one of the newly discovered planets in the TRAPPIST-1 system. Credits: NASA/JPL-Caltech

For over a century, scientists have considered the possibility that life may be distributed throughout our Universe by meteoroids, asteroids, comets, and planetoids. Similarly, multiple studies have been conducted to see if the building blocks of life could have come to Earth (and been distributed throughout the Solar System) in the same way.

Every year, an estimated 36,287 metric tons (40,000 tons) of space debris falls to Earth, and material that has been ejected from our planet is floating around out in space as well. And we know for a fact that Earth and Mars have exchanged material on several occasions, where Martian ejecta kicked up by asteroids and comets was thrown into space and eventually collided with our planet.

As such, studies like this can help us to understand how life came to be in our Solar System. At the same time, they can illustrate how in other star systems, the process may be far more intense. As Fred Ciesla – a professor of geophysical sciences at UChicago and a co-author of the paper – explained:

“Given that tightly packed planetary systems are being detected more frequently, this research will make us rethink what we expect to find in terms of habitable planets and the transfer of life—not only in the TRAPPIST-1 system, but elsewhere. We should be thinking in terms of systems of planets as a whole, and how they interact, rather than in terms of individual planets.”

Artist’s impression of the view from the most distant exoplanet discovered around the red dwarf star TRAPPIST-1. Credit: ESO/M. Kornmesser.

And with all the exoplanets discoveries made of late – which can only be described as explosive – opportunities for research are similarly exploding. In total, some 3,483 exoplanets have been confirmed so far, with an additional 4,496 candidates awaiting confirmation. Of the confirmed planets, 581 have been found to exist within multi-planet systems (like TRAPPIST-1), each of which present the possibility of litho-panspermia.

By studying more and more in the way of distant planets, we can reach beyond our own Solar System to see how planets evolve, interact, and how life can come to exist on them. And someday, we may actually be able to study them up close! One can only imagine what we may find…

Further Reading: University of Chicago, Astrophysical Journal Letters

Lithopanspermia: How Earth May Have Seeded Life on Other Solar System Bodies

With the recent discovery that Europa has geysers, and therefore definitive proof of a liquid ocean, there’s a lot of talk about the possibility of life in the outer solar system.

According to a new study, there is a high probably that life spread from Earth to other planets and moons during the period of the late heavy bombardment — an era about 4.1 billion to 3.8 billion years ago — when untold numbers of asteroids and comets pummeled the Earth. Rock fragments from the Earth would have been ejected after a large meteoroid impact, and may have carried the basic ingredients for life to other solar system bodies.

These findings, from Pennsylvania State University, strongly support lithopanspermia: the idea that basic life forms can be distributed throughout the solar system via rock fragments cast forth by meteoroid impacts.

Strong evidence for lithopanspermia is found within the rocks themselves. Of the over 53,000 meteorites found on Earth, 105 have been identified as Martian in origin. In other words an impact on Mars ejected rock fragments that then hit the Earth.

The researchers simulated a large number of rock fragments ejected from the Earth and Mars with random velocities. They then tracked each rock fragment in n-body simulations — models of how objects gravitationally interact with one another over time — in order to determine how the rock fragments move among the planets.

“We ran the simulations for 10 million years after the ejection, and then counted up how many rocks hit each planet,” said doctoral student Rachel Worth, lead author on the study.

Their simulations mainly showed a large number of rock fragments falling into the Sun or exiting the solar system entirely, but a small fraction hit planets. These estimations allowed them to calculate the likelihood that a rock fragment might hit a planet or a moon. They then projected this probability to 3.5 billion years, instead of 10 million years.

In general the number of impacts decreased with the distance away from the planet of origin. Over the course of 3.5 billion years, tens of thousands of rock fragments from the Earth and Mars could have been transferred to Jupiter and several thousand rock fragments could have reached Saturn.

“Fragments from the Earth can reach the moons of Jupiter and Saturn, and thus could potentially carry life there,” Worth told Universe Today.

The researchers looked at Jupiter’s Galilean satellites: Io, Europa, Ganymede and Callisto and Saturn’s largest moons: Titan and Enceladus. Over the course of 3.5 billion years, each of these moons received between one and 10 meteoroid impacts from the Earth and Mars.

It’s statistically possible that life was carried from the Earth or Mars to one of the moons of Jupiter or Saturn. During the period of late bombardment the solar system was much warmer and the now icy moons of Saturn and Jupiter didn’t have those protective shells to prevent meteorites from reaching their liquid interiors. Even if they did have a thin layer of ice, there’s a large chance that a meteorite would fall though, depositing life in the ocean beneath.

In the case of Europa, six rock fragments from the Earth would have hit it over the last 3.5 billion years.

It has previously been thought that finding life in Europa’s oceans would be proof of an independent origin of life. “But our results suggest we can’t assume that,” Worth said. “We would need to test any life found and try to figure out whether it descended from Earth life, or is something really new.”

The paper has been accepted for publication in the journal Astrobiology and is available for download here.

 

Earth Life Forms Ejected on Asteroid Impact Could Survive and Return Again

asteroid-impact.thumbnail.jpg

Does this mean that, perhaps, we can go home again?

If an asteroid or comet impacted Earth, the resulting ejection of materials could contain life forms. According to a study published in the journal Astrobiology, these life forms could survive and then seed another planet or moon with life. Additionally, Earth could also be re-seeded with life by those same life forms.

Ah, there’s no place like home.

If rock fragments containing embedded microorganisms were ejected into space, at least some of those organisms might survive and reseed Earth or seed another planetary surface able to support life. This scenario, which is called lithopanspermia was examined in studies called systematic shock recovery experiments designed to simulate this type of situation where microorganisms are transported between planets via meteorites.

The researchers sandwiched dry layers of three kinds of biological test ingredients, including bacterial endospores, endolithic cyanobacteria, and epilithic lichens, into rocks analogous to rocks from Mars. They then simulated the shock pressures Martian meteorites experienced when they were ejected from Mars and determined the ability of the organisms to survive the harsh conditions.

The organisms are hardy examples of microbes that can withstand extreme environmental stress and represent potential ‘hitchhikers’ within impact-ejected rocks.

“Given that impacts have occurred on planetary bodies throughout the history of our solar system,” says Sherry L. Cady, PhD, Associate Professor in the Department of Geology at Portland State University, “the hypothesis that life in rock could have been transferred between planets at different times during the past 3.5 billion years is plausible.”

And not only is it plausible that Mars rocks could be transferred to Earth and vice versa, but ejected rocks from Earth could possibly return and land back on their home planet. Given the contemplation of the destruction of life on Earth, it’s somewhat comforting to think that we could perhaps start over again from our own ingredients.

Original News Source: Astrobiology Press Release