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Weekly space gallery for January 28, 2014

WELCOME TO OUR WEEKLY COLLECTION of the best astronomy and space exploration images taken by observatories around the world and in space. Each week we’ll bring you a selection of our favourite recent images – if you like them (and we hope you do), please share them with your friends. And don’t forget you can elect to have this and other stories emailed direct to your inbox, just by signing up to our free email service – see the Subscribe box in the column at right.

So, let’s get started on this week’s images.

1. Disruptive black hole

A black hole lives at the heart of the white galaxy in the middle of this image. Extensive clouds of hot gas, detected by NASA’s Chandra X-ray Observatory satellite and coloured purple, should be the raw material from which countless new stars would be born. But jets of energy emanating from the vicinity of the black hole have disrupted the gas, forming two cavities on either side of the centre and sending out shock waves that prevent the gas from clumping and forming stars. The galaxy in question is called RX J1532+3201, and it is 3.9 billion light years from Earth. Image credit: X-ray: NASA / CXC / Stanford / J.Hlavacek-Larrondo et al, Optical: NASA / ESA / STScI / M.Postman & CLASH team.

Gas surrounding galaxy RX J1532+3201

Hot gas surrounds galaxy RX J1532+3201.

 

2. Titan, top and bottom

This black and white image of Titan, Saturn’s largest moon, was taken through a special infrared filter to bring out detail in its atmosphere. Visible at the far north (top) is a haze that stands up above the bulk of atmosphere, while near the south pole is the South Polar Vortex – thought to be an uplifted mass of air caused by a change in the seasons. This image was taken by NASA’s Cassini spacecraft from a distance of 2.5 million kilometres. Cassini has been orbiting Saturn since 2004. Courtesy NASA / JPL-Caltech / Space Science Institute.

Titan

Haze is visible in Titan’s north, while a polar vortex is in the south.

 

3. Brown dwarf revealed

Astronomers have used special techniques to block out the light of a star (leaving a speckled appearance) to reveal a dim brown dwarf that is in orbit around it. Brown dwarfs are bodies at are two big to be planets, but two small to be proper stars. They give off a relatively small amount of heat. The astronomers are particularly interested in studying the brown dwarf’s atmosphere, by analysing the light that reflects from it. “This object is old and cold and will ultimately garner much attention as one of the most well-studied and scrutinised brown dwarfs detected to date,” says Justin R. Crepp of the University of Notre Dame. “With continued follow-up observations, we can use it as a laboratory to test theoretical atmospheric models. Eventually we want to directly image and acquire the spectrum of Earth-like planets. Then, from the spectrum, we should be able to tell what the planet is made out of, what its mass is, radius, age, etc., basically all relevant physical properties.” Courtesy Crepp et al. 2014, ApJ.

Brown dwarf image

By blocking most of the light of its parent star, a faint brown dwarf is revealed.

 

4. A gallery of galaxies

The Hubble Space Telescope was used to make this long-exposure image of the galaxy cluster Abell 2744, which comprises the bright galaxies in the foreground. Fainter background galaxies appear to have become distorted as their light is bent by Abell 2744’s gravity. Astronomers have counted up to 3,000 of these background galaxies in the full-size version of this image alone. Courtesy NASA / ESA.

Galaxy cluster Abell 2744

A long Hubble exposure of galaxy cluster Abell 2744 also reveals other galaxies in the far background.

 

5. We have lift-off

NASA’s newest Tracking and Data Relay System Satellite (TDRSS) was launched on January 23 from the Kennedy Space Centre in Florida. There are several TDRSS satellites circling Earth, through which NASA can communicate with spacecraft in Earth orbit. They are not directly involved in communicating with deep space missions. Courtesy NASA / Tony Grey.

Time exposure of TDRSS launch

Lift off of NASA’s latest TDRSS satellite.

 

6. A supernova surprise

A supernova was spotted in galaxy M82 on January 21, causing great excitement amongst astronomers. M82 is only 12 million light years from Earth, making the supernova (called SN 2014J) one of the closest in many years. Many observatories broke into their normal scheduled operations to make observations of the supernova, including NASA’s Swift orbiting observatory. This picture, sensitive to ultraviolet light, shows the supernova standing out brightly against the amorphous background of the rest of M82. Courtesy NASA / Swift / P. Brown, TAMU.

Swift image of galaxy M82 and its supernova

A Swift image of galaxy M82 and its supernova.

Story by Jonathan Nally.

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Views of Moons

NASA’S CASSINI SPACECRAFT, in orbit around the planet Saturn, has been sending back some wonderful views of its moons. In particular, it has captured images where one moon seems to float in front of the other. Here we present a selection of recent images.

Cassini image of Titan and Tethys

Can you tell which of these moons in the foreground? It's Titan, the large one (diameter 5,150 kilometres; bigger than our Moon) with the orange atmosphere, with smaller, shiny, icy Tethys in the background. Titan was 2.3 million kilometres from Titan, and 3.4 million from Tethys when it took this image. Saturn's rings can be seen edge-on in the distance.

Cassini image of Rhea and Titan

This black-and-white image shows the moon Rhea (1,528 km diameter) in front of Titan. Cassini was 2 million kilometres from Titan and 1.3 million kilometres from Rhea when it took this image.

Cassini image of Titan and Dione

This view shows Titan again, this time with the much smaller moon Dione (1,123 km diameter) peering around from behind, with Saturn and its rings (edge-on) in the background. Cassini was 2.3 million kilometres from Titan and 3.2 million kilometres from Dione when it took the image. The haze that surrounds Titan can clearly be seen. Titan has a mostly nitrogen atmosphere that extends far from the surface. The surface pressure is about 1.5 times that on Earth.

Cassini image of Titan

In this view, Titan appears to float in front of Saturn and its rings. Titan is not only the second-largest moon in the Solar System; it's also about 300 kilometres wider than the planet Mercury!

More information: Cassini mission

Story by Jonathan Nally. Images courtesy NASA / JPL-Caltech / Space Science Institute.

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Gallery – Saturn’s four moon shuffle

Cassini image of four Saturnian moons

Four of Saturn's moons are visible in the image taken by NASA's Cassini spacecraft.

A QUARTET OF SATURN’S MOONS, from tiny to huge, surround and are embedded within the planet’s rings in this Cassini image. Saturn itself is out of frame to the left.

Saturn’s largest moon, Titan (5,150 kilometres wide), is in the background of the image.

Next, in the foreground is Dione (1,123 kilometres wide), with the wispy terrain on its trailing hemisphere easily visible.

The third moon is Pandora(81 kilometres wide), which orbits just beyond the rings on the right of the image.

Saturn's rings with Pan in the  Encke gap

The tiny moon Pan appears as a speck in the gap in the rings.

Finally, tiny Pan (28 kilometres wide) can just be seen as a tiny speck in the ‘Encke Gap’ of the A ring on the left of the image.

Saturn has 62 known moons, with the vast majority of them being 50 kilometres or less in diameter.

The image was taken with the Cassini spacecraft narrow-angle camera on September 17, 2011, at a distance of approximately 2.1 million kilometres from Dione.

Adapted from information issued by NASA / JPL-Caltech / Space Science Institute.

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Life on Titan: up in the air?

Titan, Epimetheus and Saturn's rings

Saturn's moon Titan looms large behind the planet's rings. (A smaller moon, Epimetheus, is in the foreground.) Chemical reactions in Titan's upper atmosphere could form molecules that are the precursor of life.

  • Titan’s atmosphere simulated in the lab
  • Chemical reactions produce amino acids
  • Key ingredients for life as we know it

While simulating possible chemical processes that could occur in the hazy atmosphere of Titan, Saturn’s largest moon, a University of Arizona-led planetary research team found amino acids and nucleotide bases in the mix—the most important ingredients of life on Earth.

“Our team is the first to be able to do this in an atmosphere without liquid water. Our results show that it is possible to make very complex molecules in the outer parts of an atmosphere,” said Sarah Hörst, a graduate student in the University of Arizona’s (UA) Lunar and Planetary Lab, who led the international research effort together with her adviser, planetary science professor Roger Yelle.

The molecules discovered include the five nucleotide bases used by life on Earth to build the genetic materials DNA and RNA: cytosine, adenine, thymine, guanine and uracil, and the two smallest amino acids, glycine and alanine. Amino acids are the building blocks of proteins.

Reaction chamber

A window into Titan’s atmosphere: Energised by microwaves, the gas mix inside the reaction chamber lights up like a pink neon sign. Thousands of complex organic molecules accumulated on the bottom of the chamber during this experiment.

The results suggest not only that Titan’s atmosphere could be a reservoir of pre-biotic molecules that serve as the springboard to life, but they offer a new perspective on the emergence of terrestrial life as well: Instead of coalescing in a primordial soup, the first ingredients of life on our planet may have rained down from a primordial haze high in the atmosphere.

Oddball of the Solar System

Titan has fascinated—and puzzled—scientists for a long time.

“It’s is the only moon in our Solar System that has a substantial atmosphere,” Hörst said. “Its atmosphere stretches out much further into space than Earth’s. The moon is smaller so it has less gravity pulling it back down.”

Titan’s atmosphere is much denser, too—on the surface, atmospheric pressure equals that at the bottom of a 5-metre-deep pool on Earth.

“At the same time, Titan’s atmosphere is more similar to ours than any other atmosphere in the Solar System,” Hörst said. “In fact, Titan has been called ‘Earth frozen in time’ because some believe this is what Earth could have looked like early in time.”

Saturn's moon Titan

Saturn's moon Titan has a thick, hazy atmosphere.

When the Voyager I spacecraft flew by Titan in the 1970s, the pictures transmitted back to Earth showed a blurry, orange ball.

“For a long time, that was all we knew about Titan,” Hörst said. “All it saw were the outer reaches of the atmosphere, not the moon’s body itself. We knew it has a an atmosphere and that it contains methane and other small organic molecules, but that was it.”

In the meantime, scientists learned that Titan’s haze consists of aerosols, just like the smog that cloaks many metropolitan areas on Earth. Aerosols, tiny particles about a quarter millionth of an inch across, resemble little snowballs when viewed with a high-powered electron microscope.

The exact nature of Titan’s aerosols remains a mystery. What makes them so interesting to planetary scientists is that they consist of organic molecules—potential ingredients for life.

“We want to know what kinds of chemistry can happen in the atmosphere and how far it can go.” Hörst said. “Are we talking small molecules that can go on to becoming more interesting things? Could proteins form in that atmosphere?”

What it takes to make life’s molecules

For that to happen, though, energy is needed to break apart the simple atmospheric molecules—nitrogen, methane and carbon monoxide—and rearrange the fragments into more complex compounds such as pre-biotic molecules.

“There is no way this could happen on Titan’s surface,” Hörst said. “The haze is so thick that the moon is shrouded in a perpetual dusky twilight. Plus, at -124 degrees Celsius, the water ice that we think covers the moon’s surface is as hard as granite.”

However, the atmosphere’s upper reaches are exposed to a constant bombardment of ultraviolet radiation and charged particles coming from the sun and deflected by Saturn’s magnetic field, which could spark the necessary chemical reactions.

Smog-like particles

Tiny particles are thought to create the smog-like haze that enshrouds Saturn's moon Titan.

To study Titan’s atmosphere, scientists have to rely on data collected by the spacecraft Cassini, which has been exploring the Saturn system since 2004 and flies by Titan every few weeks on average.

“With Voyager, we only got to look,” says Hörst. “With Cassini, we get to touch the moon a little bit.”

During fly-by manoeuvres, Cassini has gobbled up some of the molecules in the outermost stretches of Titan’s atmosphere and analysed them with its on-board mass spectrometer. Unfortunately, the instrument was not designed to unravel the identity of larger molecules—precisely the kind that were found floating in great numbers in Titan’s mysterious haze.

“Cassini can’t get very close to the surface because the atmosphere gets in the way and causes drag on the spacecraft,” Hörst said. “The deepest it went was 900 kilometres (560 miles) from the surface. It can’t go any closer than that.”

To find answers, Hörst and her co-workers had to recreate Titan’s atmosphere here on Earth. More precisely, in a lab in Paris, France.

“Fundamentally, we cannot reproduce Titan’s atmosphere in the lab, but our hope was that by doing these simulations, we can start to understand the chemistry that leads to aerosol formation,” Hörst said. “We can then use what we learn in the lab and apply it to what we already know about Titan.”

Like a spy in a movie

Hörst and her collaborators mixed the gases found in Titan’s atmosphere in a stainless-steel reaction chamber and subjected the mixture to microwaves causing a gas discharge—the same process that makes neon signs glow—to simulate the energy hitting the outer fringes of the moon’s atmosphere.

The electrical discharge caused some of the gaseous raw materials to bond together into solid matter, similar to the way UV sunlight creates haze on Titan. The synthesis chamber, constructed by a collaborating group in Paris, is unique because it uses electrical fields to keep the aerosols in a levitated state.

“The aerosols form while they’re floating there,” Hörst explains. “As soon as they grow heavy enough, they fall onto the bottom of the reaction vessel and we scrape them out.”

“And then,” she added, “the samples went on an adventure.”

To analyse the aerosols, Hörst had to use a high-resolution mass spectrometer in a lab in Grenoble, about a three-hour ride from Paris on the TGV, France’s high-speed train.

“I always joke that I felt like [I was in ] a spy in a movie because I would take our samples, put them into little vials, seal them all up and then I’d get on the TGV, and every 5 minutes I’d open the briefcase, ‘Are they still there? Are they still there?’ Those samples were really, really precious.”

Analysing the reaction products with a mass spectrometer, the researchers identified about 5,000 different molecular formulas.

Sarah Hörst

“When I came back and looked at the screen, I thought: That can’t be right,” said graduate student Sarah Hörst.

“We really have no idea how many molecules are in these samples other than it’s a lot,” Hörst said. “Assuming there are at least three or four structural variations of each, we are talking up to 20,000 molecules that could be in there. So in some way, we are not surprised that we made the nucleotide bases and the amino acids.”

“The mass spectrometer tells us what atoms the aerosols are made of, but it doesn’t tell us the structure of those molecules,” Hörst said. “What we really wanted to find out was, what are all the formulas in this mass spectrum?”

“On a whim, we said, ‘Hey, it would be really easy to write a list of the molecular formulas of all the amino acids and nucleotide bases used by life on Earth and have the computer go through them.’”

“I was sitting in front of my computer one day—I had just written up the list—and I put the file in, hit ‘Enter’ and went to go do something,” she said. “When I came back and looked at the screen, it was printing a list of all the things it had found and I sat there and stared at it for a while. I thought: That can’t be right.”

“I ran upstairs to find Roger, my adviser, and he wasn’t there,” Hörst said with a laugh. “I went back to my office, and then upstairs again to find him and he wasn’t there. It was very stressful.”

“We never started out saying, ‘we want to make these things,’ it was more like ‘hey, let’s see if they’re there.’ You have all those little pieces flying around in the plasma, and so we would expect them to form all sorts of things.”

In addition to the nucleotides, the elements of the genetic code of all life on Earth, Hörst identified more than half of the molecular formulas for the 22 amino acids that life uses to make proteins.

Titan: A window into Earth’s past?

In some way, Hörst said, the discovery of Earth’s life molecules in an alien atmosphere experiment is ironic.

Here is why: The chemistry occurring on Titan might be similar to that occurring on the young Earth that produced biological material and eventually led to the evolution of life. These processes no longer occur in the Earth’s atmosphere because of the large abundance of oxygen cutting short the chemical cycles before large molecules have a chance to form. On the other hand, some oxygen is needed to create biological molecules. Titan’s atmosphere appears to provide just enough oxygen to supply the raw material for biological molecules, but not enough to quench their formation.

“There are a lot of reasons why life on Titan would probably be based on completely different chemistry than life on Earth,” Hörst added, “one of them being that there is liquid water on Earth. The interesting part for us is that we now know you can make pretty much anything you want in an atmosphere. Who knows this kind of chemistry isn’t happening on planets outside our Solar System?”

Adapted from information issued by UA / S. Hörst / NASA.

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Moons with a view

NASA’s Cassini spacecraft has been orbiting Saturn since July 2004. The ringed planet has more than 60 moons, and Cassini has taken numerous images of them.

Sometimes, when the angles are just right, Cassini’s camera can fit more than one moon into its field of view—with one moon in the background and one in the foreground.

Many of the moons orbit near or within the planet’s famous rings, so the rings often appear in the images too.

Here’s a selection of recent shots showing some of Saturn’s natural satellites, large and small.

Rhea, Prometheus and Saturn's rings

In this view, the moon Rhea (1,530km wide) is on the far side of the rings. Much smaller Prometheus (86km wide) is on the nearside, orbiting between the main portion of the rings and the thin outer F ring. Camera distance to Rhea: approx. 1.6 million km. Camera distance to Prometheus: approx. 1 million km.

Dione and Titan

The cratered and cracked moon Dione (1,120km wide) seems to hang suspended in place in front of Titan (5,150km wide) in the background. Camera distance to Dione: approx 1.8 million km. Camera distance to Titan: approx. 2.7 million km.

Tethys and Dione

Dione, in the foreground of this image, appears darker than the moon Tethys (1,070km wide). Tethys appears brighter because it has a higher albedo than Dione, meaning Tethys reflects more sunlight. Camera distance to Dione: approx. 1.2 million km. Camera distance to Tethys: 1.8 million km.

Epimetheus and Janus

Saturn's moon Epimetheus (86km wide) moves in front of the larger moon Janus (179km wide) as seen by the Cassini spacecraft. Camera distance to Epimetheus: approx. 2.1 million km. Camera distance to Janus: 2.2 million km.

Janus and Prometheus

In this image, Janus is on the far side of Saturn's rings. Prometheus is on the nearside, orbiting in the gap between the main rings and the outer, thin F ring. Camera distance to Janus: approx. 1.1 million km. Camera distance to Prometheus: 1 million km.

Images courtesy of NASA / JPL / Space Science Institute.

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Titan gets a visitor

Artist's impression of Cassini passing Titan

NASA's Cassini probe will conduct a close fly-by of Titan on July 7, swooping to within about 1,000 kilometres of its surface.

NASA’s Cassini spacecraft is to conduct a close fly-by of Titan, Saturn’s largest moon, on July 7. The craft will swoop to within 1,005 kilometres of the cloud-covered world, shooting past at a speed of 5.9 km per second (21,240km/h or 13,000mph).

During the close approach, instruments will study the chemical make-up of its atmosphere, while Cassini’s radar will scan a poorly-covered region of the moon. Other instruments will keep an eye on clouds in Titan’s atmosphere.

A black and white view of Titan

A black and white view of Titan, showing the dark region known as Senkyo.

Ice world with a thick atmosphere

In many respects Saturn’s largest moon is one of the most Earth-like worlds found to date. With its thick atmosphere and organic-rich chemistry, Titan resembles a frozen version of Earth, several billion years ago, before life began pumping oxygen into our atmosphere.

Titan is of great interest to scientists because it has a substantial, active atmosphere and complex, Earth-like processes that shape its surface. The moon is enveloped by an orange haze of naturally produced photochemical smog that frustratingly obscured its surface prior to Cassini’s arrival. Since 2004, the spacecraft’s observations have taken the study of this unique world into a whole new dimension.

Cassini has revealed that Titan’s surface is shaped by rivers and lakes of liquid ethane and methane (the main component of natural gas), which forms clouds and occasionally rains from the sky as water does on Earth. Winds sculpt vast regions of dark, hydrocarbon-rich dunes that girdle the moon’s equator and low latitudes. Volcanism may occur as well, but with liquid water as the lava.

First landing in the outer Solar System

Rounded river rocks on Titan and Earth.

Rounded river rocks on Titan (left) and Earth.

On its journey to Saturn, Cassini carried the European-built Huygens probe. On January 14, 2005, Huygens achieved humankind’s first landing on a body in the Outer Solar System when it parachuted through Titan’s murky skies. Huygens took measurements of atmospheric composition and wind speeds during its decent, along with an incredible series of images showing telltale patterns of erosion by flowing liquid. The probe came to rest on what appeared to be a floodplain, surrounded by rounded cobbles of water ice.

As the now-renamed Cassini Equinox Mission progresses, the spacecraft will monitor Titan’s atmosphere and surface for signs of seasonal change. The spacecraft’s radar and camera systems will continue to peer through the haze, expanding high-resolution maps of the surface. And scientists will eagerly await new data that could confirm the presence of a liquid ocean beneath the giant moon’s surface.

Adapted from information issued by NASA / JPL / Space Science Institute / ESA / University of Arizona / S.M. Matheson.

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Shadows on Saturn

The shadows of Enceladus (left) and Titan (right) on Saturn's cloud tops.

The shadows of Enceladus (left) and Titan (right) on Saturn's cloud tops.

These two views from NASA’s Cassini spacecraft, currently in orbit around Saturn, show the huge difference in scale between it’s largest Moon, Titan, and a smaller one, Enceladus—even though the moons themselves are not in view.

On the left is a view taken with Saturn”s rings almost edge-on. On the planet’s clouds, just below the rings, can be seen a dark spot—this is the shadow being cast by Enceladus. The moon itself is a long way off to the left and not visible in this frame. Enceladus is about 500 kilometres in diameter.

On the right is another view with almost the same geometry, but this time there is a huge shadow on Saturn’s clouds, stretched out by the curve of the planet. This is the shadow of Titan, Saturn’s largest planet and one that is currently the target of many investigations.

Titan has a thick, nitrogen atmosphere, similar to what Earth’s atmosphere is thought to have been like billions of years ago. Titan is 10 times bigger than Enceladus, with an average diameter of 2,576 kilometres.

A view of the surface of Titan, taken by the Huygens probe

A view of the surface of Titan, taken by the Huygens probe after it landed on January 14, 2005

On January 14, 2005, the Huygens probe—which had been carried by Cassini all the way from Earth—descended through Titan’s clouds and landed safely on its surface. It found a frozen world, but one that sometimes experiences rain and rivers of methane and ethane at super-cold temperatures.

In just a couple of days from now, July 7, Cassini will make another close fly-by of Titan—swooping over the moon at a distance of only 1,005 kilometres—and will train its suite of instruments on the thick clouds and frozen surface.

The left-hand view above was taken from a distance of around 1.7 million kilometres from Saturn, while the right-hand view was from around 2.1 million kilometres.

Story by Jonathan Nally, Editor, SpaceInfo.com.au

Images courtesy NASA / JPL / Space Science Institute.

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Moon gases: life starters?

Titan, Saturn’s largest moon

To simulate sunlight hitting Titan's atmosphere to see what chemicals were produced, researchers zapped nitrogen and methane in a laboratory with high-energy UV light. Shown here are some of Saturn's rings, the tiny moon Epimetheus, and the much larger Titan in the background.

  • Exposing nitrogen and methane to UV light
  • Resulted in nitrogen-containing “brown gunk”
  • Such chemicals might be found on Saturn’s moon Titan

The first experimental evidence showing how atmospheric nitrogen can be incorporated into organic macromolecules has been reported by a University of Arizona (UA) team.

The finding suggests the type of organic molecules that might be found on Titan, the moon of Saturn that scientists think is a model for the chemistry of pre-life Earth.

Earth and Titan are the only known planetary-sized bodies that have thick, predominantly nitrogen atmospheres, said Hiroshi Imanaka, who conducted the research while a member of UA’s chemistry and biochemistry department.

How complex organic molecules become “nitrogenated” in settings like early Earth or Titan’s atmosphere is a big mystery, Imanaka said.

“Titan is so interesting because its nitrogen-dominated atmosphere and organic chemistry might give us a clue to the origin of life on our Earth,” said Imanaka, now an assistant research scientist in the UA’s Lunar and Planetary Laboratory. “Nitrogen is an essential element of life.”

Nitrogen fluorescing blue under UV light

Nitrogen fluorescing blue under UV light

Smog world could hide life

However, not just any nitrogen will do. Nitrogen gas must be converted to a more chemically active form that can drive the reactions that form the basis of biological systems.

Imanaka and Mark Smith converted a nitrogen-methane gas mixture similar to Titan’s atmosphere into a collection of nitrogen-containing organic molecules by irradiating the gas with high-energy UV rays. The laboratory set-up was designed to mimic how solar radiation affects Titan’s atmosphere.

Most of the nitrogen moved directly into solid compounds, rather than gaseous ones, said Smith, a UA professor and head of chemistry and biochemistry. Previous models predicted the nitrogen would move from gaseous compounds to solid ones in a lengthier stepwise process.

Titan looks orange in colour because a smog of organic molecules envelops the planet. The particles in the smog will eventually settle down to the surface and may be exposed to conditions that could form life, said Imanaka, who is also a principal investigator at the SETI Institute.

However, scientists don’t know whether Titan’s smog particles contain nitrogen. If some of the particles are the same nitrogen-containing organic molecules the UA team created in the laboratory, conditions conducive to life are more likely, Smith said.

Laboratory observations such as these indicate what the next space missions should look for and what instruments should be developed to help in the search, Smith said.

Brown gunk held the key

The UA researchers wanted to simulate conditions in Titan’s thin upper atmosphere because results from the Cassini Mission indicated “extreme UV” radiation hitting the atmosphere created complex organic molecules.

Therefore, Imanaka and Smith used the Advanced Light Source at Lawrence Berkeley National Laboratory’s synchrotron in Berkeley, California, to shoot high-energy UV light into a stainless steel cylinder containing nitrogen-and-methane gas held at very low pressure.

Hiroshi Imanaka inside the Advanced Light Source

Hiroshi Imanaka stands next to the experiment inside the Advanced Light Source

The researchers used a mass spectrometer to analyse the chemicals that resulted from the radiation.

Simple though it sounds, setting up the experimental equipment is complicated. In addition, many researchers want to use the Advanced Light Source, so competition for time on the instrument is fierce. Imanaka and Smith were allocated one or two time slots per year, each of which was for eight hours a day for only five to 10 days.

Completing all the necessary experiments took years.

At the beginning, they analysed only the gases from the cylinder. But he didn’t detect any nitrogen-containing organic compounds.

Imanaka and Smith thought there was something wrong in the experimental set-up, so they tweaked the system. But still no nitrogen.

“It was quite a mystery,” said Imanaka. “Where did the nitrogen go?”

Finally, the two researchers collected the bits of brown gunk that gathered on the cylinder wall and analysed it with what Imanaka called “the most sophisticated mass spectrometer technique.”

Imanaka said, “Then I finally found the nitrogen!”

Imanaka and Smith suspect that such compounds are formed in Titan’s upper atmosphere and eventually fall to Titan’s surface. Once on the surface, they contribute to an environment that is conducive to the evolution of life.

Adapted from information issued by University of Arizona / Hiroshi Imanaka / Doug Archer / NASA / JPL / Space Science Institute.

Life on Titan could eat acetylene

Artist's concept of a lake on the surface of the moon Titan

This artist concept shows a mirror-smooth lake on the surface of the smoggy moon Titan. Cassini scientists have concluded that at least one of the large lakes observed on Saturn's moon Titan contains liquid hydrocarbons, and have positively identified ethane. This result makes Titan the only place in our Solar System beyond Earth known to have liquid on its surface.

  • Chemicals are disappearing on Titan
  • Could be food for primitive life

Strange chemistry on Saturn’s moon Titan could indicate the presence of primitive life, say scientists.

While non-biological chemistry offers one possible explanation, some scientists believe the chemical indications bolster the argument for a primitive, exotic form of life or precursor to life on Titan’s surface.

One key finding shows hydrogen molecules flowing down through Titan’s atmosphere and disappearing at the surface. Another is that maps of hydrocarbons on the surface show a lack of acetylene, commonly known as welding gas.

The lack of acetylene is important because that chemical would likely be the best energy source for a methane-based life on Titan, said Chris McKay, an astrobiologist at NASA Ames Research Centre, who proposed a set of conditions necessary for this kind of methane-based life on Titan in 2005.

One interpretation is that the acetylene is being consumed as food. But McKay said the flow of hydrogen is even more critical because all of the proposed life mechanisms involved the consumption of hydrogen.

Titan as seen by the Cassini spacecraft

Saturn's moon Titan is very cold and smothered in hydrocarbon smog.

“We suggested hydrogen consumption because it’s the obvious gas for life to consume on Titan, similar to the way we consume oxygen on Earth,” McKay said. “If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from water-based life on Earth.”

Life in deep-freeze

To date, methane-based life forms are only hypothetical. Scientists have not yet detected this form of life anywhere, though there are liquid-water-based microbes on Earth that thrive on methane or produce it as a waste product.

On Titan, where temperatures are around 90 Kelvin (minus 283 degrees Celsius), a methane-based organism would have to use a substance that is liquid for living processes, but not water itself. Water is frozen solid on Titan’s surface and much too cold to support life as we know it.

“Scientific conservatism suggests that a biological explanation should be the last choice after all non-biological explanations are addressed,” said Mark Allen, principal investigator with the NASA Astrobiology Institute Titan team.

“We have a lot of work to do to rule out possible non-biological explanations. It is more likely that a chemical process, without biology, can explain these results—for example, reactions involving mineral catalysts.”

Adapted from information issued by NASA / JPL.

Life on Titan would be smelly

An artist's impression of methane-Ethane lakes on Titan.

An artist's impression of methane-ethane lakes on Titan.

Research by astrobiologist William Bains suggests that if life has evolved on the frozen surface of Saturn’s moon, Titan, it would be strange, smelly and explosive compared to life on Earth.

“Hollywood would have problems with these aliens” said Dr Bains. “Beam one onto the Starship Enterprise and it would boil and then burst into flames, and the fumes would kill everyone in range. Even a tiny whiff of its breath would smell unbelievably horrible.”

“But I think it is all the more interesting for that reason,” he adds. “Wouldn’t it be sad if the most alien things we found in the galaxy were just like us, but blue and with tails?”

Dr Bains will present his work at the Royal Astronomical Society (RAS) National Astronomy Meeting, which begins on Monday at the University of Glasgow. His research, which is carried out through Rufus Scientific in Cambridge, UK, and MIT in the USA, is seeking to work out just how extreme the chemistry of life can be.

Life on Titan, Saturn’s largest moon, represents one of the more bizarre scenarios being studied.

Titan is twice as large as our Moon and has a thick atmosphere of frozen, orange smog. At ten times our distance from the Sun, it is a frigid place, with a surface temperature of -180 degrees Celsius. Water is permanently frozen into ice and the only liquid available is liquid methane and ethane, which the Cassini/Huygens mission has shown is present in ponds and lakes on the surface of the moon.

“Life needs a liquid; even the driest desert plant on Earth needs water for its metabolism to work,” said Dr Bains. “So, if life were to exist on Titan, it must have blood based on liquid methane, not water. That means its whole chemistry is radically different.

Saturn's largest moon, Titan.

Saturn's largest moon, Titan, is covered by thick clouds.

“The molecules must be made of a wider variety of elements than we use, but put together in smaller molecules. It would also be much more chemically reactive,” Dr Bains said.

Life needs the right chemicals

The solubility of chemicals in liquid methane is very limited, and strongly dependent on molecular weight. With a few exceptions, molecules with more than 6 heavy (non-hydrogen) atoms are essentially insoluble. So a metabolism running in liquid methane will have to be built of smaller molecules than terrestrial biochemistry, which is typically built of modules of around 10 heavy atoms.

However you can only build around 3400 molecules from such a small number of atoms if you are limited to the chemistry that terrestrial life uses, ie. carbon, nitrogen, oxygen, and sulphur and phosphorus in very limited chemical contexts.

Dr Bains explained, “Terrestrial life uses about 700 molecules, but to find the right 700 there is reason to suppose that you need to be able to make 10 million or more. The issue is not how many molecules you can make, but whether you can make the collection you need to assemble a metabolism.”

“It is like trying to find bits of wood in a lumber-yard to make a table. In theory you only need 5. But you may have a lumberyard full of off-cuts and still not find exactly the right five that fit together. So you need the potential to make many more molecules than you actually need.”

“Thus the 6-atom chemicals on Titan would have to include much more diverse bond types and probably more diverse elements, including sulphur and phosphorus in much more diverse and (to us) unstable forms, and other elements such as silicon.”

Energy is another factor that would affect the type of life that could evolve on Titan. With Sunlight a tenth of a percent as intense on Titan’s surface as on the surface of Earth, energy is likely to be in short supply.

“Rapid movement or growth needs a lot of energy, so slow-growing, lichen-like organisms are possible in theory, but velociraptors are pretty much ruled out,” said Bains.

Adapted from information issued by the RAS. Images courtesy NASA / JPL / Space Science Institute / Karl Kofoed.