Where to search for signs of life on Titan

July 20, 2018 by Julia Demarines, Astrobiology Magazine
Looking down at Titan with Cassini. Some of the large lakes filled with methane and ethane are visible through the haze. Credit: NASA/JPL–Caltech/SSI.

New findings, published in the journal Astrobiology, suggest that large craters are the prime locations in which to find the building blocks of life on Saturn's largest moon, Titan.

Titan is an icy expanse covered by organic molecules, with liquid methane lakes enshrouded by a thick, hazy atmosphere of nitrogen and methane that begs the question: why isn't there life on this strangely Earth-like world? Perhaps it is the balmy –179 degrees Celsius (-300 degrees Fahrenheit) temperatureon the surface that would likely prevent any biochemical reactions from taking place. But is there any place on Titan where there might be hope that biomolecules, such as amino acids, could form? One team wanted to find out.

Using imagery and data from the Cassini spacecraft and Huygens probe, scientists led by Dr. Catherine Neish, a planetary scientist specializing in impact cratering at the University of Western Ontario, went on a hunt for the best places to look for biological molecules on the surface of Titan. Life, as we know it, is carbon-based and uses liquid as a solvent. The surface of Titan has abundant carbon-rich molecules (hydrocarbons) that have been shown to form amino acids, the building blocks of proteins needed for life, when exposed to liquid water in laboratory simulations.

Herein lies the problem: Titan is much too cold for liquid water to be present on the surface. Although this is not a favorable scenario for life-bearing molecules to form, there is hope.

Erasing craters

Radar measurements from Cassini, which orbited Saturn for 13 years, were able to peer through Titan's optically thick atmosphere, revealing the terrain of this enigmatic world. What was revealed was unexpected – Titan is active. Cassini's radar instrument unveiled lakes, dunes, mountains, river valleys, and not many craters, indicating that there are processes happening that resurface Titan and either fill in or erode older craters. Discovering a similar world to Earth over nine times its distance from the Sun was monumental.

With such a familiar landscape to Earth, where would be the best places to look for signs of life? Although the methane lakes may have seemed like the obvious choice, Neish and her colleagues instead found craters and cryovolcanoes (regions where liquid water erupts from beneath Titan's icy surface) to be the two most enticing locations. Both features hold promise for melting Titan's icy crust into liquid water, a necessary step to form complex biomolecules.

Dr. Morgan Cable, a technologist in the Instrument Systems Implementation and Concepts Section at NASA's Jet Propulsion Laboratory, in Pasadena, California, is an expert in 'tholins' (organics produced when simple gas mixtures are subject to cosmic radiation). She commented, "when we mix tholins with liquid water we make really fast. So any place where there is liquid water on Titan's surface or near its surface could be generating the precursors to life – biomolecules – that would be important for life as we know it, and that's really exciting."

Sotra Facula is a cryovolcano on Titan. This image, built from radar topography with infrared colors overlaid, shows the volcano’s caldera, mountainous peaks and thin, bright flows away from the cryovolcano. Credit: NASA/JPL–Caltech/USGS/University of Arizona

Craters are best

With both cryovolcanoes and craters as literal hot spots for melting on Titan, which feature is the one that you should bet your money on? For Neish, the answer is unequivocally craters, despite there not being as many on Titan as there are on our Moon.

"Craters really emerged as the clear winner for three main reasons," Neish tells Astrobiology Magazine. "One, is that we're pretty sure there are craters on Titan.

Cratering is a very common geologic process and we see circular features that are almost certainly craters on the surface," she says.

The second point is that craters would likely generate more melt than a cryovolcano, meaning that "they take longer to freeze so [the water] will stay liquid for longer," says Neish, adding that is key for complex chemical reactions to take place.

"The last point is that should produce water that's at a higher temperature than a cryovolcano," says Neish. Hotter water means faster chemical reaction rates, which holds promise for the creation of life-bearing molecules.

"Water could stay liquid in those environments for thousands of years, or even longer," says Cable.

Cryovolcanoes, on the other hand, are not so hot. "When a cryovolcano erupts, it typically erupts right at the melting temperature of the ice, and we think any 'lava' [in this case, a slushy form of water] on Titan would be heavily doped with ammonia, which suppresses the freezing point quite a bit so that would make the lava pretty cold," says Neish.

Sotra Facula is a cryovolcano on Titan. This image, built from radar topography with infrared colors overlaid, shows the volcano’s caldera, mountainous peaks and thin, bright flows away from the cryovolcano. Credit: NASA/JPL–Caltech/USGS/University of Arizona

To put the final nail into the coffin for these icy volcanoes', cryovolcanism turns out to be a more obscure and elusive process. Imagine ice, which is less dense than water, floating in a glass of water. "Trying to get the water up on the top of the ice is quite difficult when you have a density contrast like that," says Neish. "Cryovolcanism is the harder thing to do and there is very little evidence of it on Titan."

In fact, cryovolcanism might not even be real on Titan. "Sotra Facula[a mountainous feature on Titan that appears to have a caldera-like depression] is perhaps the best and only example that we have of a cryovolcano on Titan." adds Neish. "So it's much rarer, if it exists at all."

In situ measurements

Sinlap (112 kilometers/70 miles in diameter), Selk (90 kilometers/56 miles), and Menrva (392 kilometers/244 miles) craters, which are the largest fresh craters on Titan, are prime locations in which to look when we finally have the capabilities to search for biomolecules in these craters. A probe would need to land on Titan and take in situmeasurements to make such a discovery. But are these targets the next candidates for a future Titan mission? Not everyone is convinced.

"We don't know where to search even with results like this," says Dr. David Grinspoon, a Senior Scientist at the Planetary Science Institute. "I wouldn't use it to guide our next mission to Titan. It's premature."

Instead, Grinspoon wants to sniff out more places on Titan. "Because there is so little that we actually know about the planet, it makes more sense to characterize a range of environments first," he says.

Nevertheless, although Titan is perplexing, the search for life's building blocks on this frigid world needs to start somewhere and the result of this research gives us not one, but three potential candidates for where to start that search, with hopefully many more to come.

Explore further: Changes in Titan's surface brightness point to cryovolcanism

More information: Catherine D. Neish et al. Strategies for Detecting Biological Molecules on Titan, Astrobiology (2018). DOI: 10.1089/ast.2017.1758

Related Stories

Changes in Titan's surface brightness point to cryovolcanism

September 14, 2013

Changes in surface brightness on Titan observed over four years by NASA's Cassini spacecraft have added to evidence that cryovolcanism is active on Saturn's largest Moon. Anezina Solomonidou has presented results at the European ...

Titan gets a dune 'makeover'

January 17, 2013

(Phys.org)—Titan's siblings must be jealous. While most of Saturn's moons display their ancient faces pockmarked by thousands of craters, Titan - Saturn's largest moon - may look much younger than it really is because its ...

Cassini nears 100th Titan flyby with a look back

March 6, 2014

(Phys.org) —Ten years ago, we knew Titan as a fuzzy orange ball about the size of Mercury. We knew it had a nitrogen atmosphere—the only known world with a thick nitrogen atmosphere besides Earth. But what might lie beneath ...

Cassini heads toward final close encounter with Titan

April 19, 2017

NASA's Cassini spacecraft will make its final close flyby of Saturn's haze-enshrouded moon Titan this weekend. The flyby marks the mission's final opportunity for up-close observations of the lakes and seas of liquid hydrocarbons ...

Counting Titan's Craters

April 22, 2010

Impact craters found on Titan could help scientists determine the age of this Earth-like moon and its potential for life.

Recommended for you

Unusual doughnut-shaped jet observed in the galaxy NGC 6109

August 15, 2018

Astronomers from the University of Bristol, U.K., have uncovered an unusual doughnut-shaped jet in the radio galaxy NGC 6109. It is the first time that such a jet morphology has been observed in a low-power radio galaxy. ...

Iron and titanium in the atmosphere of an exoplanet

August 15, 2018

Exoplanets, planets in other solar systems, can orbit very close to their host stars. When the host star is much hotter than the sun, the exoplanet becomes as hot as a star. The hottest "ultra-hot" planet was discovered last ...

Unraveling the stellar content of young clusters

August 14, 2018

About twenty-five percent of young stars in our galaxy form in clustered environments, and stars in a cluster are often close enough to each other to affect the way they accrete gas and grow. Astronomers trying to understand ...

32 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

rrwillsj
2 / 5 (4) Jul 20, 2018
It is not just a moral question of risking contamination the speculated biome of Titan. Since many commentators have made it clear that the moral values they claim? Are always superseded by their greed & craving for public acclaim.

Destroying the very thing they are greedily intent upon is a lousy way to do business. In addition, sending one or two landers will have a very limited range of exploration & collection.

The best scenario for exploring Titan would be to start with an orbiting automated assembly facilities using space resources collected & delivered by robot trawlers. Then send a fleet of orbiters & landers to Titan. With the capacity & capability of methodical, planet wide exploration.

Some idiots have expressed a desire that possibly alien life found on Mars or Titan, be brought to Earth for research.

No! Hell No!! And most explicitly, Fucking Hell No!!!

The orbiting facilities could be re-purposed to provide safe laboratories for remote research.
antialias_physorg
5 / 5 (5) Jul 20, 2018
While we should take care not to contaminate another potential biosphere I also think we shouldn't be overly paranoid about it. Titan isn't hospitable to stuff evolved on Earth - and even so: anything evolved on Titan will have such an unadapted thing as our Earth bacteria for lunch (and vice versa if any microbes from Titan get to Earth)
TheGhostofOtto1923
4 / 5 (2) Jul 20, 2018
While we should take care not to contaminate another potential biosphere I also think we shouldn't be overly paranoid about it. Titan isn't hospitable to stuff evolved on Earth - and even so: anything evolved on Titan will have such an unadapted thing as our Earth bacteria for lunch (and vice versa if any microbes from Titan get to Earth)
Probably, but not undoubtedly. The dense biosphere on earth may provide the sort of enhanced competition that has given rise to some superior form factor or evolutionary breakthrough that hasnt had the chance to evolve elsewhere.

Humans are one example of this potential.

Terror birds reigned supreme for millions of years until a land bridge introduced canines into their environment. The pack was something they never had to evolve.
wduckss
1.7 / 5 (6) Jul 20, 2018
"Scientists have pinpointed the lowest temperature at which simple life can live and grow.

The study, published in PLoS One, reveals that below -20 °C, single-celled organisms dehydrate, sending them into a vitrified – glass-like – state during which they are unable to complete their life cycle.

The researchers propose that, since the organisms cannot reproduce below this temperature, -20 °C is the lowest temperature limit for life on Earth." https://phys.org/...ife.html
Temperature of Titan moon is 93.7 K (−179.5 °C).
Whether "scientists" look for life or brainless readers?
DavidDcomments
3.5 / 5 (2) Jul 21, 2018
The precursor molecules to life are likely created in comets. Enceladus Europa and Titan could all possibly have life. Mars might even have microbial life of some sort. In the case of Mars I believe we should start terraforming it as soon as possible with terrestrial microbes since the process will take centuries.
granville583762
4 / 5 (4) Jul 21, 2018
Is -180C degrees precursor to interplanetary travelling life?
wduckss> The study, published in PLoS One, reveals that below -20 °C, single-celled organisms dehydrate, sending them into a vitrified – glass-like – state during which they are unable to complete their life cycle

You didn't say if you take the single-celled organisms down to titans balmy the balmy –179C degrees Celsius and hold it there for a month then bring it back to room temperature to see whether the single-celled organisms can stand -179C degrees and when conditions permit come back to life.

In other words is the vitrified –20C degree glass-like – state during which they are unable to complete their life cycle the death knell of no return for the single-celled organism!
rrwillsj
1 / 5 (3) Jul 21, 2018
DDc, if you believe that the possibility of Mars Life? How do you morally justify committing genocide upon a biome that has survived billions of years?

Just to make a quick buck? Selling tickets to suckers who do not comprehend the consequences to themselves or their descendants. Forcibly imprisoned on a junk failed planet.

If greed is your motivation? Consider avoiding the waste of destroying an alien Living World. Protecting, cherishing, researching non-Earth lifeforms promises huge dividends for thoughtful investment.

If all there is are micro-organisms? That does not mean you are entitled in your egotistical affluenza to destroy the possibility of their unknown future. That Mars native life evolving further over the next few billion years.

As our Sun swells into a Red Giant Star. And the Earth is a dead clinker? Could be when Mars Life might flourish beyond our wildest comicbook fantasies.
Surveillance_Egg_Unit
3.7 / 5 (3) Jul 22, 2018
DDc, if you believe that the possibility of Mars Life? How do you morally justify committing genocide upo
n a biome that has survived billions of years?

Just to make a quick buck? Selling tickets to suckers who do not comprehend the consequences to themselves or their descendants. Forcibly imprisoned on a junk failed planet.

If greed is your motivation? Consider avoiding the waste of destroying an alien Living World. Protecting, cherishing, researching non-Earth lifeforms promises huge dividends for thoughtful investment.

If all there is are micro-organisms? That does not mean you are entitled in your egotistical affluenza to destroy the possibility of their unknown future. That Mars native life evolving further over the next few billion years.

As our Sun swells into a Red Giant Star. And the Earth is a dead clinker? Could be when Mars Life might flourish beyond our wildest comicbook fantasies.

says the latter-day Carrie Nation
Thorium Boy
1 / 5 (3) Jul 22, 2018
Problem with exploration to find life is chronology. You send a probe to Mars, to look for life. It finds nothing. 10 years later, you send another probe. You find life. Wow! Except what you might have found was carried by the first probe from Earth to Mars.
rrwillsj
1 / 5 (2) Jul 22, 2018
S_E_U, Thank you for the compliment. If I leave any impression upon the audience of these entertainment commentaries?

I want it to be... "PUT DOWN THE DAMN COMICBOOKS AND DO SOMETHING CONSTRUCTIVE WITH YOUR LIFE!"

Those who despise the ideals of morals and ethics? Will live down to the lowest level of their expectations.
TopCat22
2.3 / 5 (3) Jul 22, 2018
Titan is the most hospitable body in our solar system besides Earth. Protection there is a good quality Down Parka with a scuba helmet and a scuba tank to add oxygen for breathing would do.

The climate there is not much more difficult to work with than Antarctica.

Has every needed natural resource and much more easily accessible and in greater abundance that we can need and use to survive.

It is much smaller than mars so easier to land and take off from.

Why is Mars colonisation being pushed so much when Titan would be a much more hospitable place?
wduckss
not rated yet Jul 22, 2018
@granville583762
https://www.ncbi....3686811/
https://www.resea...on_Earth

The article I quoted was published by phys.org.
If you have more precise and credible evidence, please attach the link.
Before that, you show form: how a micro organism emerged at -180 ° C? With Earth?
Mark Thomas
5 / 5 (3) Jul 22, 2018
Titan is the most hospitable body in our solar system besides Earth.


If we are talking about hospitable for humans, then I disagree. Titan is cryogenicly cold (−180 °C, -290 °F ), dark (1% sunlight) and its gravity (0.14 g) is weaker than our moon's gravity (0.166 g). https://en.wikipe...n_(moon)

Mars is the most hospitable body for humans in our solar system besides Earth.

Interesting, I might agree with your statement billions of years from now when the sun has swelled up, but who knows?
torbjorn_b_g_larsson
5 / 5 (3) Jul 22, 2018
I think Grinssoon is too harsh, early search filters help formulate later derivations.

It is not just a moral question of risking contamination the speculated biome of Titan. Since many commentators have made it clear that the moral values they claim? Are always superseded by their greed & craving for public acclaim.


We cannot "contaminate" a foreign biome, likely not even eradicate it if we wanted too, c.f. 4 Gyrs of Earth biome.

What commentators and what values do you mean? Certainly not on this thread, you were first. As for scientists in general, they are not greedier (say, more corrupt) than others, and as for morals greed is what drives our beneficial economy. And of course science is *based* on a meritocracy, else it wouldn't work! If you promise to stay off the internet to not be seen as a hypocrite, be free to criticize science meritocracy all you want.

torbjorn_b_g_larsson
5 / 5 (3) Jul 22, 2018
Titan is the most hospitable body in our solar system besides Earth.


If we are talking about hospitable for humans, then I disagree.


Me too. Antarctica has one attempt to colony (by Argentina) by the way, but in practice it is "a" research station because it is too hard to colonize - not a good example!
torbjorn_b_g_larsson
5 / 5 (3) Jul 22, 2018
Except what you might have found was carried by the first probe from Earth to Mars.


Yes, but that is easily sorted out by genetic methods. It is more of a problem of contaminating measurements.
Mark Thomas
5 / 5 (3) Jul 22, 2018
What commentators and what values do you mean? Certainly not on this thread, you were first.


rrwillsj has a long history of wildly exaggerating and simply making stuff up just so he can refute it. For example, NASA is well aware of the potential problems of forward and backward contamination. Nobody is suggesting we simply throw caution to the wind and ignore these issues.
TopCat22
3 / 5 (2) Jul 22, 2018
Mars is the most hospitable body for humans in our solar system besides Earth.


You are wrong there.

On Titan you can walk around the surface without a heavy space suit. You need only thermal insulation (a decent parka or heated underwear to go jogging) and an oxygen tank for breathing.

The atmospheric surface pressure is earth-like so your blood wont boil in you veins, freeze dry you skin, and cosmic ray your cells like on Mars without a heavy pressure space suit.

Mars has no dense atmosphere. Titan you can grab an ice rock off the ground to drink, grow food or make oxygen and fuel
wduckss
not rated yet Jul 23, 2018
@TopCat22
Where do you see O2 and H2O?

Titan moon Atmosphere
Surface pressure
146.7 kPa (1.45 atm)

Composition by volume Variable
Stratosphere:
98.4% nitrogen (N2),
1.4% methane (CH4),
0.2% hydrogen (H2);

Lower troposphere:
95.0% N
2, 4.9% CH4;
97% N
2, 2.7±0.1% CH4, 0.1–0.2% H2
http://www.svemir...hydrogen
TopCat22
3 / 5 (2) Jul 23, 2018
The solid rocks, sand and mountains of Titan are made of mostly Pure Water Ice. You melt the ice for H2O and make all the O2 you need from that

Atmospheric pressure of 1.45 atm on the surface is the key figure that makes it most habitable. You can walk around without a space suit. Just need very good thick wool underwear under your jeans to go for a walk.
wduckss
not rated yet Jul 23, 2018
The Cassini–Huygens mission was not equipped to provide evidence for biosignatures or complex organic compounds; .. atmosphere on Titan, with the important exception of a lack of water vapor on Titan. Wiki

First, you have to understand that ice is not just from H2O. There are: nitrogen ice, CH4 ice, dry ice CO2 etc.
O2 melt point is -218.79 ° C, boiling point -182 962 ° C.
If there's O2 on Titan we would have discovered it in the atmosphere because temperature Titan moon is -179.5 ° C (above the boiling point of O2).
Evidence or empty stories?
TopCat22
5 / 5 (1) Jul 23, 2018
How long would I survive on Titan without a spacesuit?
Todd Gardiner, Updated Jul 14, 2015 · Author has 26.6k answers and 26.8m answer views

Well, the surface air pressure is 1.45x of that found on Earth, and nearly entirely made of nitrogen. The remaining 4% is methane, which is not toxic to humans. Anything else is just a trace gas. But there isn't any oxygen to breathe, so you are going to suffocate.

The temperature on the surface is a very chilly −179.2 °C, so you can't just stand around in street clothes. In fact, your lungs would freeze trying to breathe the nitrogen atmosphere.

So, if you had protection from the cold and your own air, you could live indefinitely. If your use of the term "spacesuit" was meant to be a suit that survives in the vacuum of space, you don't need a pressure suit, just insulation and a standard oxygen mask mixing O2 into heated Titan air.
Ojorf
not rated yet Jul 23, 2018
^^^
You forgot the best part, humans can fly on Titan and we all want to fly.

https://en.wikipe...n#Flight
TopCat22
not rated yet Jul 23, 2018
^^^
You forgot the best part, humans can fly on Titan and we all want to fly.

https://en.wikipe...n#Flight


I forgot ... on Titan it would be similar to being in 10 feet of water. You can basically swim in the air there like a fish in water (or fly like a bird in the air with some wing material attached to your arms and legs to flap)
TheGhostofOtto1923
not rated yet Jul 23, 2018
Why is Mars colonisation being pushed so much when Titan would be a much more hospitable place?
Because we cant get there right now. We can get to mars. But we will be living beneath the surface on both worlds anyway.
Mark Thomas
5 / 5 (1) Jul 23, 2018
Just need very good thick wool underwear under your jeans to go for a walk.


Ha! I would love to see your face after you have been deposited onto the surface of Titan with nothing more than wool underwear under your jeans and an oxygen tank. The thickness of the atmosphere is actually working against you at 290 degrees below zero F because it will drain the heat out of your body very quickly and painfully. Keep in mind that nitrogen liquefies at ~320 degrees below zero, so Titan is more than just "chilly." Maybe you could try lighting your exhaled breath on fire for warmth if it happens to be raining liquid methane, but I would not recommend it. :-)

https://www.quora...clothing
wduckss
5 / 5 (1) Jul 23, 2018
Beautiful life in a huge tank of nitrogen at -180 ° C!
Walt Dizney is in a similar bottle, do you want it too?
Technology (already) exists here on Earth. Make your stories, stay for a few days in the tank of frozen nitrogen at -180 ° C.
https://www.thesu...we-know/
TheGhostofOtto1923
5 / 5 (1) Jul 23, 2018
Me too. Antarctica has one attempt to colony (by Argentina) by the way, but in practice it is "a" research station because it is too hard to colonize - not a good example!
I dunno - I would consider this a colony
https://www.youtu...iVT23MhA

-Although not self-sufficient, it was not really designed to be so.

Population
• Total
Summer: 150
Winter: 45
rrwillsj
3 / 5 (2) Jul 23, 2018
t_b_g_l, please look out your window & point in the direction of a chestnut tree. Are you ready to replace your family's dog with a pet cane toad? Tumbleweed? Lampreys? Tree Borers? Any of these ring a bell?

Earth Life had a good run for a few billion years... And now humans are making a great effort, to destroy the Earth's biosphere.

Cause why not? It proves our "superiority" that we are both physically & psychologically capable, of committing Matricide.

And I never criticized the scientists. That is you diverting with an ad hominem attack to avoid the issue.

The real issue is is that perpetually childish attitude of yourself & many of the other commentators (see above) that you can disregard reality, playing at conquering the galaxy. Without any serious consequences.

Cause you read it in a comicbook and that makes your delusions absolute truth!

If you are incompetent to sustain the Earth? When will you ever be competent to colonize the planets?

wduckss
not rated yet Jul 24, 2018
@rrwillsj
For comment 5 of me, except "And I never criticized the scientists. That is you diverting with an ad hominem attack to avoid the issue. "
Is scientist in the service of the progress of mankind if the story empty stories without evidence? If this is done just for propaganda, self-presentation and malicious distortion of real evidence?
rrwillsj
1 / 5 (1) Jul 24, 2018
good question wduckss. How do you intend to prove your contention that 'real evidence' is available that counters the conclusions of the research team in this article?

Have you presented your 'real evidence' to peer review? With results verified and confirmed by any recognized authority?

Are you being a good citizen and reporting what you consider bogus data to the involved professional bodies and educational institutions?
wduckss
not rated yet Jul 24, 2018
For this article I have included sufficient evidence (for those who want to read and understand).

My works (where and when they are published) can be viewed on my page http://www.svemir...ion.html
In particular, see the article (I against "science") http://www.svemir...ion.html#no-ring-around-Pluto as well as http://www.svemir...ion.html#Hubbles-law etc …
Evidence and only evidence.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.