Messy Chemistry: A New Way to Approach the Origins of Life

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Astrobiologist and chemist Irena Mamajanov and prebiotic chemist Kuhan Chandru in their messy chemistry garb at the Earth-Life Science Institute (ELSI) in Tokyo. Mamajanov leads an effort at the institute to study a new “messy” path to understanding how some prebiotic chemical systems led to building blocks of life on early Earth. (Nerissa Escanlar)

More than a half century ago, Stanley Miller and Harold Urey famously put water and gases believed to make up the atmosphere of early Earth into a flask with water, sparked the mix with an electric charge, and produced amino acids and other chemical building blocks of life.

The experiment was hailed as a ground-breaking reproduction of how the essential components of life may have been formed, or at least a proof of concept that important building blocks of life could be formed from more simple components.

Little discussed by anyone outside the origins of life scientific community was that the experiment also produced a lot of a dark, sticky substance, a gooey tar that covered the beaker’s insides. It was dismissed as largely unimportant and regrettable then, and in the thousands of parallel origins of life experiments that followed.

Today, however, some intrepid researchers are looking at the tarry residue in a different light.

Tarry residue from an experiment — a common result when organic compounds are heated.

Just maybe, they argue, the tar was equally if not more important as those prized amino acids (which, after all, were hidden away in the tar until they were extracted out.) Maybe the messy tar – produced by the interaction of organic compounds and an energy source — offers a pathway forward in a field that has produced many advances but ultimately no breakthrough.

Those now studying the tar call their research “messy chemistry,” as opposed to the “clean” chemistry that focused on the acclaimed organic compounds.

There are other centers where different versions of “messy chemistry” research are under way — including George Cody’s lab at the Carnegie Institution for Sciences and Nicholas Hud’s at the Georgia Institute of Technology — but it is probably most concentrated at the Earth-Life Science Institute in Tokyo (ELSI.)

There, messy chemistry is viewed as an ignored but promising way forward, and almost a call to arms.

“In classical origin-of-life synthetic chemistry and biology you’re looking at one reaction and analyzing its maximum result. It’s A+B = C+D,” said Irena Mamajanov, an astrobiologist with a background in chemistry who is now a principal investigator ELSI and head of the overall messy chemistry project.

“But life is not like that; it isn’t any single reaction. They’re looking at a subset of reactions and we ask: ‘Why not look at the whole complex system?’”

 

Irena Mamajanov of ELSI, with colleague Yuki Suna, synthesizes particular complex molecules similar to enzymes to explore the many pathways that could have been involved in the production of actual early enzymes. The term “messy chemistry” grew out of an prebiotic chemistry conference at the Carnegie Institution of Science in Washington several years ago.  (Nerissa Escanlar)

There’s a scientific lineage here – researchers have worked with complex systems and reaction systems in many fields, and in principle this is the same. It’s taking a “systems” approach and applying it to that black box period on Earth when non- biological chemicals were slowly transformed (or transformed themselves) into chemical systems with the attributes of “life.”

The messy chemistry work is getting noticed, and Mamajanov was a featured speaker on the “New Approaches to the Origins of Life” plenary at the 2017 Astrobiology Science Conference, in Mesa, Arizona. At ELSI alone, researchers have been working on messy chemistry using metals, using electricity, using radioactivity, using computational chemistry and using analytical chemistry to tease out patterns and structure in the tars.

Mamajanov says this messy chemistry approach – which she learned to some extent as a fellow at both Carnegie and Georgia Tech — makes intuitive, as well as scientific sense because life is nothing if not complex.

Wouldn’t it be logical for the origin of life to be found in some of the earliest complex systems on Earth. rather than in looking for straight-line processes that progress almost independent of all the chemistry happening around them?

It stands to reason that the gunky tar played a role, she said, because tars allow some essential processes to occur. Tars can concentrate compounds, can encapsulate them, and can provide a kind of primitive (messy) scaffolding that could eventually evolve into the essential backbones of a living entity.

 

Stanley Miller and the iconic Miller-Urey experiment in 1952. The experiment added some of the chemicals thought to be in the Early Earth atmosphere, some water, and an electric charge. The result was the creation of some building blocks of life (amino acids, nucleotides) and lots of what was long considered a problematic residue of tar.

It’s the structure, in fact, that stands out as a particularly promising aspect of messy chemistry. More traditional synthetic biology is looking for simple molecular structures created by clean reactions, while messy chemistry is doing the opposite.

The goal of messy chemists is to see what interesting chemical processes take place within a defined portion of the messy, complex sample. What unexpected, surprising compounds or chemical structures might be formed? And how might they shed light on the process of chemical self-organization and more generally the origin of life question?

In her lab on the basement floor of the ELSI main building, Mamajanov works with colleagues to synthesize her messy molecules and push further into understanding their structures, their potential ability to adapt, and their suitability as possible precursors to the RNA and DNA molecules that characterize life.

Her specific area of study is hyperbranched polymers – three-dimensional, tree-shaped chains of repeating molecules that connect with other similar molecules. The result is globular, presents multitudes of chemical reactions and has some hidden and protected spaces inside their globs.  Related synthetic, or bio-mimicked chemicals (i.e., modeled on biological compounds and processes) have been used by the drug industry for some time.

With these hyperbranched polymers, Mamajanov has worked to produce pathways within the messy systems where the polymers show characteristics of evolvability.

Hyperbranch polymers exist in nature, most prominently in the process that petroleum oil is form, but are also made synthetically for research.  The tar that Mamajamov makes out of the chemicals is greasy but clear rather than brownish.

Her hyperbranched polymers are synthetic, as are those of noted synthetic chemists–in-search-of-biology such as Steven Benner, at the Foundation for Applied Molecular Evolution and Gerald Joyce of the Scripps Institute.

But the starting points are quite different, as are the goals. The two men are working to create clean chemical systems that produce the building block molecules that they want, but without the tar.  Mamajamov is intentionally making tar.

Eric Smith, a specialist in complexity systems, physics and chemistry who is also at ELSI sees the messy approach as containing the seeds of an important new way forward. “What is now called messy chemistry used to be completely out of the mainstream,” he said. “That is no longer the case.”

Smith described how John Sutherland of the Laboratory of Molecular Biology at Cambridge, U.K. won accolades for his work on the prebiotic assembly of important building blocks for RNA, using controlled chemistry that avoided all the messiness.

But he was also criticized later for using a such a controlled model – early Earth, after all, did not have any outside controller – and Smith said Sutherland is incorporating the messier side of prebiotic chemistry today, although tar remains an enemy rather than a potential friend.

“Now he’s going back to a one pot synthesis, allowing reactions that would have to be less controlled than what he was doing before,” Smith said of Sutherland. “He may do it in a way quite different from Irena and others involved in messy chemistry, but it seems to allow for many more complex reactions.”

Eric Smith is a senior scientist at ELSI steeped in the world of complex systems. (Nerissa Escanlar)

And complexity is indeed the desired endpoint. Not simply repetitive reactions and not random ones, but rather reactions that are very complex but ultimately structured.

This is where another novel aspect of the messy chemistry approach comes into play: Mamajanov and others at ELSI are collaborating with practitioners of “artificial chemistry,” computer simulated versions of what could be happening in messy interactions.

The work is being done primarily by Nathaniel Virgo, an artificial life specialist who uses computing to learn about how chemical systems behave once you leave the laboratory world where the number of chemical components is small and controlled.

And his big question: “Are there situations in which you can get ‘order from disorder’ in chemistry – to start with a messy system and have it spontaneously become more ordered? If so, what kinds of conditions are required for this to happen, and what kinds of ordered states can result?

Mamajanov needs Virgo’s computations to analyze and project forward what a messy chemical system might do, since the sheer number of possible chemical reactions involved is huge. And Virgo needs the messy chemistry as a test bed of sorts for his abstracted questions about, in effect, making order out of what appears to be chaos. They are, for each other, hypothesis-generating machines.

Virgo pointed to several primary reasons why computational work is important for answering the question of creating order from disorder (and ultimately, he is convinced, life from non-life.)

“The first is simply that studying messy chemistry experimentally is really hard. If you have a test tube containing a mess, it takes a lot of work to find out what molecules are in it, and basically impossible to know what reactions are happening, at least not without an enormous amount of work. In contrast, in a simulation you know exactly what molecules and reactions are present, even if there are millions of different types.”

Nathaniel Virgo, a specialist in computational artificial-life, speaks during an ELSI seminar in Tokyo.  (Nerissa Escanlar)

The second reason involves the fundamental issue of studying specific chemical systems versus studying general mechanisms.

“As a complex systems scientist, I first want to know what, in general, is required, for a given phenomenon to occur. Once this is known, it should become clear which real systems will exhibit the right kinds of properties.

“This allows us to narrow down the vast space of possible hypotheses for the origins of life, rather than simply testing them one at a time. It should also give us some insight into the question of whether life might be possible with completely different kinds of chemistry than the protein-nucleic acid-metabolite chemistry we have on Earth.

From his studies he has found that in messy chemical systems, chemical self-production occurs and tht the systems can change dramatically in response to small changes such as an increased temperature.

“This suggests that messy chemistry is fundamentally qualitatively different from clean chemistry – adding more species doesn’t just mean the system gets harder to study, it also means that fundamentally new things can happen.”

And in the origins of life world, things are happening.

 

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Cassini Nearing the End, Still Working Hard

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Spiral density wave on Saturn’s moon Janus. (NASA/JPL-Caltech)

As the Cassini mission embarks on its final dive this Friday into Saturn, it will continue taking photos all the way down (or as far as it remains operations.)

We’ve grown accustomed to seeing remarkable images for the mission and the planet, but clearly the show is not over, and perhaps far from it.

This is what NASA wrote describing the image above:

This view  shows a wave structure in Saturn’s rings known as the Janus 2:1 spiral density wave. Resulting from the same process that creates spiral galaxies, spiral density waves in Saturn’s rings are much more tightly wound. In this case, every second wave crest is actually the same spiral arm which has encircled the entire planet multiple times.

This is the only major density wave visible in Saturn’s B ring. Most of the B ring is characterized by structures that dominate the areas where density waves might otherwise occur, but this innermost portion of the B ring is different.

For reasons researchers do not entirely understand, damping of waves by larger ring structures is very weak at this location, so this wave is seen ringing for hundreds of bright wave crests, unlike density waves in Saturn’s A ring.

The image gives the illusion that the ring plane is tilted away from the camera toward upper-left, but this is not the case. Because of the mechanics of how this kind of wave propagates, the wavelength decreases with distance from the resonance. Thus, the upper-left of the image is just as close to the camera as the lower-right, while the wavelength of the density wave is simply shorter.

This wave is remarkable because Janus, the moon that generates it, is in a strange orbital configuration. Janus and Epimetheus (see PIA12602) share practically the same orbit and trade places every four years. Every time one of those orbit swaps takes place, the ring at this location responds, spawning a new crest in the wave.

The distance between any pair of crests corresponds to four years’ worth of the wave propagating downstream from the resonance, which means the wave seen here encodes many decades’ worth of the orbital history of Janus and Epimetheus.

According to this interpretation, the part of the wave at the very upper-left of this image corresponds to the positions of Janus and Epimetheus around the time of the Voyager flybys in 1980 and 1981, which is the time at which Janus and Epimetheus were first proven to be two distinct objects (they were first observed in 1966).

Epimetheus also generates waves at this location, but they are swamped by the waves from Janus, since Janus is the larger of the two moons.

 

The clouds covering the planet itself consist of ammonia ice.  Further down is also some water ice, some ammonium hydrosulfide ice, and further still is ammonia in a gas phase. Some cloud layers are more than 1000 miles thick. (NASA/JPL-Caltech.

This image is from a few months ago, but it certainly puts you there above the deep, deep clouds of Saturn.  False color was used to make the patterns more discernible.

Saturn has some remarkable features in its atmosphere. When the Voyager missions traveled to the planet in the early 1980s, it imaged a hexagon-shaped cloud formation near the north pole. Twenty-five years later, infrared images taken by Cassini revealed the storm was still spinning, powered by jet streams that push it to speeds of about 220 mph (100 meters per second). At 15,000 miles  across, the long-lasting storm could easily contain an Earth or two.

Cassini is now on its last full orbit, to be following by its partial finale.  The final 22 orbits leading to the plunge into the clouds looked like this:

Cassini’s final orbits, in blue, have taken the spacecraft closer to the planet than ever before, and into the space between the rings and the top of the cloud layers. (NASA/JPL-Caltech)

 

And here is a Jet Propulsion Lab video recapping the Cassini mission and describing its Friday rendezvous:

 

(NASA/JPL-Caltech)

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Is That the Foundation of NASA I Feel Shifting?

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A lunar outpost was an element of the George W. Bush era Vision for Space Exploration, which has been replaced with President Barack Obama’s space policy. The outpost would have been an inhabited facility on the surface of the Moon. At the time it was proposed, NASA was to construct the outpost over the five years between 2019 and 2024. Now the man nominated to be the next NASA administrator, James Bridenstine, is a strong and vocal advocate of building a moon colony.  (NASA)

Reading about some of the views coming from the man recently nominated to become NASA’s Administrator, Rep. James Bridenstine of Oklahoma, I heard the sound of a door closing.

Other doors will surely be opened if he is confirmed by the Senate, but that shutting door happens to be to the gateway to a realm that has engrossed and nurtured me and clearly many millions of Americans.

What is happening, I fear, is that our Golden Age of space science, of exploration for the sake of expanding humanity’s knowledge and wonder, is about to wind down.  The James Webb Space Telescope will (probably) still be launched, and missions to Europa and Mars are on the books.  But to be a Golden Age there must be an on-going vision for the future building on what has been accomplished.

When it comes to space science, that clearly takes strong government support and taxpayer money.  And if what I’m reading is correct, a lot of that future NASA funding for exploring and understanding the grand questions of space science will be going instead to setting up and maintaining that colony on the moon.

And the goals Bridenstine appears to have in mind when he speaks of setting up a moon colony are decidedly military, strategic and commercial.  As when Vice President Mike Pence spoke to NASA workers at the Kennedy Space Center to telegraph the Trump Administration’s space vision, space science is essentially an afterthought.

Media coverage of the Bridenstine selection has tended to focus on the fact that he’s a politician and that he has earlier been quite critical of climate change science.

But what concerns me most are his views about space science in general.  Because with the money and focus a major moon colony project would take, NASA’s space science initiatives run the risk of returning to the back seat they occupied in the agency’s earlier days.

Rep. Jim Bridenstine, R-Okla., addresses the Space Symposium in Colorado Springs in 2016. (Tom Kimmell)

A former jet pilot, director of the Tulsa Air and Space Museum and an early supporter of then candidate Donald Trump, Bridenstine has been clear for a long time about his priorities in space.  I think we have to assume they correspond to the views of those in the White House.

In a speech last year to the Lunar Exploration Group titled This is Our Sputnik Moment,”  he pointed to what he described as a major missed opportunity the mid 1990s “discovery” of water at the poles of the moon by a Defense Department mission.  (It was actually a Navy-NASA mission that first made the detection, and it hinted at the presence of water rather than proving anything. The proof came later via missions by NASA, the Japanese space agency, the Chinese space agency and perhaps most important, the Indian space agency.)

Here are excerpts from the talk he gave, which I am quoting at length to to give a better feel for his mindset and for the kind of change he is proposing.  These are points consistent with talks he has given many times before and are memorialized in his proposed American Space Renaissance Act.   American space activities, he makes clear, should focus first and foremost on cis-lunar space, the area between the moon and Earth.

“This single discovery” of frozen water on the moon, he said, “should have immediately transformed America’s space program. Water ice not only represents a critical in situ resource for life support (air and water); it can be cracked into its components, hydrogen and oxygen, to create the same chemical propellant that powered the Space Shuttle.

“From the discovery of water ice on the moon until this day, the American objective should have been a permanent outpost of rovers and machines at the poles with occasional manned missions for science and maintenance. The purpose of such an outpost should have been to utilize the materials and energy of the moon to drive down the costs and increase the capabilities of cis-lunar space. Let’s talk about why.

“The watershed discovery of lunar ice happened at a time when space was transforming all of our lives, ” he continued. “Today, our very way of life depends on space. We have transformed how we communicate, navigate, produce food and energy, conduct banking, predict weather, perform disaster relieve, provide security, and so much more.

“Each of these market segments continues to grow and improve the human condition on Earth, but a 2013 study by the Inter-Agency Space Debris Coordination Committee determined that the debris population in low earth orbit will continue to grow due to collisions even if nothing new is launched. Catastrophic collisions such as Iridium 33-Cosmos 2251 [which took place in 2009] will occur every five to nine years. Each such collision will create thousands of pieces of debris and result in more collisions.”

With so many satellites and much debris in low-earth orbit, Bridenstine said, it has become increasingly hazardous to send up multi-million and billion-dollar satellites.  One way to limit the congestion, he said, is to make satellites fly higher and live longer, and that means getting them additional fuel to stay on course.  The way to do that, he argues, is to gear up that envisioned water-cracking facility on the moon to produce the hydrogen to refuel satellites.   A potentially reasonable series of points.

Spent space satellites and debris, including that from a Chinese missile fired in 2007 that broke up one of the nation’s older weather satellites, are making low-Earth orbiting more hazardous.  Can hydrogen fuel from cracked water ice on the moon help break the logjam by servicing satellites further from Earth and allowing them to orbit for longer periods of time?  (NASA)

Then comes what would be a real game-changer:

“This is only possible because of all the risk that the government has already retired for these capabilities. Now, the U.S. government should play a part in developing the tools for lunar energy resource development, cis-lunar satellite servicing, and maintenance. The U.S. government must work to retire risk, make the operations routine, and once again empower commercial companies.

In other words, the U.S. government and presumably NASA should do the heavy lifting to create (and fund) this architecture so that commercial companies — among others — can profit from it.

This investment, he said, “has already worked to an extent in low Earth orbit, and now we should apply this model to cis-lunar space. This is not only appropriate for economic development and to improve the human condition on Earth, but to provide for national security, which is now entirely dependent on space-based capabilities. Every domain of warfare today depends on space.

“Once the cis-lunar market develops to service and maintain our traditional space-based military and commercial capabilities, other opportunities will naturally follow. The surface of the moon is composed mainly of oxides of metals: iron, magnesium, aluminum, silicon, titanium and others.

Raw platinum

“While these oxides can be used to produce oxygen for life support and metals for additive manufacturing in situ, they will not likely be exported to earth. However, it is possible, if not likely, that highly valuable platinum group metals are much more available on the moon from astroblemes than they are on earth.

“Such a discovery with cis-lunar transportation capabilities would fundamentally transform American commercial lunar development and could profoundly alter the economic and geopolitical balance of power on Earth. This could explain the Chinese interest in the moon. The question is: What are WE, the United States, doing to make sure the free world participates economically in such a discovery? The U.S. government has a role to play here.

“Competition for locations on the moon (the poles) and resources is inevitable. It must be stated that constitutionally, the U.S. government is required to provide for the common defense. This includes defending American military assets in space AND commercial assets in space, many of which have and will have a dual role of providing commercial and military capabilities. President Kennedy said, ‘Whatever men shall undertake, free men must fully share.’

“The U.S. government must establish a legal framework and be prepared to defend private and corporate rights and obligations all within keeping the Outer Space Treaty. And to enable freedom of action, the United States must have cis-lunar situational awareness, a cis-lunar presence, and eventually must be able to enforce the law through cis-lunar power projection. Cis-lunar development will either take the form of American values with the rule of law, or it will take the form of totalitarian state control. The United States can decide who leads.”

This image of the moon’s north polar region was taken by the Lunar Reconnaissance Orbiter Camera, or LROC. One of the primary scientific objectives of LROC is to identify regions of permanent shadow and near-permanent illumination. Since the start of the mission, LROC has acquired thousands of Wide Angle Camera images approaching the north pole. From these images, scientists produced this mosaic, which is composed of 983 images taken over a one month period during northern summer. This mosaic shows the pole when it is best illuminated, regions that are in shadow are candidates for permanent shadow, and possibly H2O. (NASA/GSFC/Arizona State University)

So this is where a moon colony leads us as viewed by a proponent: to a day when satellites and spacecraft can be fueled with lunar hydrogen while in space, but also with potential turf wars on the moon over the source of that precious hydrogen fuel.  To an expansion of American might and power to meet the perceived need to dominate space between Earth and the moon. And to a desire to exploit the moon for platinum and potentially other riches.

The only references I’ve seen from Bridenstine about space science are that a moon colony could be a good refueling and take-off point for travel to deeper space, and the belief that while sending humans to Mars should be a long-range vision, it isn’t going to happen anytime soon.  In fairness, it must be said that Bridenstine has pretty consistently voted in favor of NASA space science projects in the past,  and he has not shown hostility towards planetary or orbiting observatory missions.  But that was before there was a costly moon colony infrastructure to potentially build.

In some ways a NASA U-turn like this was almost inevitable.  The agency that made its historic mark with the Apollo program has been, with limited exceptions, out of the humans-to-space business for years.  Rockets and capsules to change this are on their way, and many possible uses for this very powerful and very costly equipment has been debated for some time.

All the while,  in the place of human exploration of space has been the phenomenal success of the space science program — with its grand observatories like the Hubble (and soon the James Webb Space Telescope), unmanned mission such as Cassini (to Saturn) and Juno (to Jupiter) and New Horizons  (to Pluto,) ground-breaking surveys of the exoplanet world by Kepler, and the now five years of Curiosity roving on Mars.

All have been immensely popular with the public by any measure, and I like to think they helped people understand much better the world in which we live.  But the missions are clearly less appealing to commercial, military and generally strategic forces that seem to want a very different kind of American space program.

Our overall national space effort has always spent more on the military side than the civilian, and NASA has also obviously played a role that is both geopolitically and militarily important.

But at its heart, NASA has for some time been about exploring and better understanding the planets and exoplanets and stars and galaxies of our universe (those Many Worlds,) and thereby enriching, enormously, I believe, life here on Earth.

The cis-lunar vision of Bridenstine and others may fail to get off the drawing boards, rather like the Obama Administration’s plan to capture and pull an asteroid towards Earth where astronauts could learn how to live and work in deep space.

But change is in the air, and the selection of Bridenstine is a pretty clear sign of how and where the winds are blowing.

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Cassini Inside the Rings of Saturn

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Movie produced from images taken while Cassini flew inside the rings of Saturn – a first. (NASA/JPL-Caltech/Space Science Institute)

The triumphant Cassini mission to Saturn will be coming to an end on September 15, when the spacecraft dives into the planet.  Running out of fuel, NASA chose to end the mission that way rather than run the risk of having the vehicle wander and ultimately land on Europa or Enceladus, potentially contaminating two moons very high on the list of possible habitable locales in our solar system.

Both the science and the images coming back from this descent are (and will be) pioneering, as they bring to an end one of the most successful and revelatory missions in NASA history.

As NASA promised, the 22-dive descent has already produced some of the most compelling images of Saturn and its rings.  Most especially, Cassini has delivered the remarkable 21-image video above.  The images were taken over a four minutes period on August 20 using a wide-angle camera.

The spacecraft captured the images from within the gap between the planet and its rings, looking outward as the spacecraft made one of its final dives through the ring-planet gap as part of the finale.

The entirety of the main rings can be seen here, but due to the low viewing angle, the rings appear extremely foreshortened. The perspective shifts from the sunlit side of the rings to the unlit side, where sunlight filters through.

On the sunlit side, the grayish C ring looks larger in the foreground because it is closer; beyond it is the bright B ring and slightly less-bright A ring, with the Cassini Division between them. The F ring is also fairly easy to make out.

 

NASA’s Cassini spacecraft will make 22 orbits of Saturn during its Grand Finale, exploring a totally new region between the planet and its rings. NASA/JPL-Caltech

While the Cassini team has to keep clear of the rings, the spacecraft is expected to get close enough to most likely answer one of the most long-debated questions about Saturn: how old are those grand features, unique in our solar system?

One school of thought says they date from the earliest formation of the planet, some 4.6 billion years ago. In other words, they’ve been there as long as the planet has been there.

But another school says they are a potentially much newer addition. They could potentially be the result of the break-up of a moon (of which Saturn has 53-plus) or a comet, or perhaps of several moons at different times. In this scenario, Saturn may have been ring-less for eons.

As Curt Niebur, lead program scientist at NASA headquarters for the Cassini mission, explained it, the key to dating the rings is a close view of, essentially, how dirty they are. Because small meteorites and dust are a ubiquitous feature of space, the rings would have significantly more mass if they have been there 4.6 billion years. But if they are determined to be relatively clean, then the age is likely younger, and perhaps much younger.

“Space is a very dirty place, with dust and micro-meteorites hitting everything. Over significant time scales this stuff coats things. So if the rings the rings are old, we should find very dirty ice. If there is little covering of the ice, then the rings must be young. We may well be coming to the end of a great debate.”

 

Cassini gazes across the icy rings of Saturn toward the icy moon Tethys, whose night side is illuminated by Saturnshine, or sunlight reflected by the planet. Tethys was on the far side of Saturn with respect to Cassini here; an observer looking upward from the moon’s surface toward Cassini would see Saturn’s illuminated disk filling the sky. Tethys was brightened by a factor of two in this image to increase its visibility. A sliver of the moon’s sunlit northern hemisphere is seen at top. A bright wedge of Saturn’s sunlit side is seen at lower left. (NASA/JPL-Caltech/Space Science Institute)

A corollary of the question of the age of Saturn’s rings is, naturally, how stable they are.

If they turn out to be as old as the planet, then they are certainly very stable.  But if they are not old then it is entirely plausible that they could be a passing phenomenon and will some day disappear — to perhaps re-appear after another moon is shattered or comet arrives.

Another way of looking at the rings is that they may well have been formed at different times.

As project scientist Linda Spilker explained in an email, Cassini’s measurements of the mass of the rings will be key.  “More massive rings could be as old as Saturn itself while less massive rings must be young.  Perhaps a moon or comet got too close and was torn apart by Saturn’s gravity.”

The voyage between the rings will also potentially provide some new insights into the workings of the disks present at the formation of all solar systems.

“The rings can teach us about the physics of disks, which are huge rings floating majestically and with synchronicity  around the new sun,” Niebur said.  “That said, the rings of Saturn have a very active regime, with particles and meteorites and micrometeorites smacking into each other.  It’s an amazing environment and has direct relevance to the nebular model of planetary formation.”

The view above was acquired at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 140 degrees. . The distance to Tethys was about 930,000 miles (1.5 million kilometers).

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA and the imaging operations center is based at the Space Science Institute in Boulder, Colorado.

 

Polar region of Saturn, with tumultuous cloud pattern. A bizarre six-sided feature encircling the north pole of Saturn was identified earlier using the visual and infrared mapping spectrometer on NASA’s Cassini spacecraft.(NASA/JPL-Caltech/Space Science Institute)

Among the areas of greatest interest during the final descent are the turbulent clouds on the North Pole of Saturn.  Cassini captured this view of the pole on April 26, 2017 – the day it began its grand finale — as it approached the planet for its first dive through the gap between the planet and its rings.

Although the pole is still bathed in sunlight at present, northern summer solstice on Saturn occurred on May 24, 2017, bringing the maximum solar illumination to the north polar region. Now the Sun begins its slow descent in the northern sky, which eventually will plunge the north pole into Earth-years of darkness. Cassini’s long mission at Saturn enabled the spacecraft to see the Sun rise over the north, revealing that region in great detail for the first time.

This view looks toward the sunlit side of the rings from about 44 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers.

Saturn boasts some unique features in its atmosphere. When the Voyager missions traveled to the planet in the early 1980s, it imaged a hexagon-shaped cloud formation near the north pole.

Twenty-five years later, infrared images taken by Cassini revealed the storm was still spinning, powered by jet streams that push it to speeds of about 220 mph (100 meters per second). At 15,000 miles (25,000 km) across, the long-lasting storm could easily contain an Earth or two.

The recent view was obtained at a distance of approximately 166,000 miles (267,000 kilometers) from Saturn.

But because Saturn is a gas giant and has no defined surface per se, it’s difficult to describe exactly how far from the planet Cassini might be traveling at any given time.

On the final orbit, Cassini will plunge into Saturn’s atmosphere, sending back new and unique science to the very end. After losing contact with Earth, the spacecraft will burn up like a meteor, becoming part of the planet itself.

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Of White Dwarfs, “Zombie” Stars and Supernovae Explosions

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Artistic view of the aftermath of a supernova explosion, with an unexpected white dwarf remnant. These super-dense but no longer active stars are thought to play a key role in many supernovae explosion. (Copyright Russell Kightley)
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White dwarf stars, the remnant cores of low-mass stars that have exhausted all their nuclear fuel, are among the most dense objects in the sky.
 
Their mass is comparable to that of the sun, while their volume is comparable to that of Earth. Very roughly, this means the average density of matter in a white dwarf would be on the order of 1,000,000 times greater than the average density of the sun.
 
Thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star — a category that includes the sun and over 97% of the other stars in the Milky Way — they are dim objects first identified a century ago but only in the last decade the subject of broad study.
 
In recent years the white dwarfs have become more and more closely associated with supernovae explosions, though the processes involved remained hotly debated.  A team using the Hubble Space Telescope even captured  before and after images of what is hypothesized to be an incomplete white dwarf supernova.  What was left behind has been described by some as a “zombie star.”
 
Now a team of astronomers led by Stephane Vennes of the Czech Academy of Sciences has detected another zombie white dwarf, LP-40-365 , that they put forward as a far-flung remnant of a long-ago supernova explosion.  This is considered important and unusual because it would represent a first detection of such a remnant long after the supernova conflagration.
 
This dynamic is well captured in an animation accompanying the Science paper that describes the possible remnant.  Here’s the animation and a second-by-second description of what is theorized to have occurred:
 
 
00.0 sec: Initial binary star outside the disk of the Milky Way galaxy. A massive white dwarf accreting
material through an accretion disk from its red giant companion star. The stars orbit around the center of
mass of the binary system.
 
14.6 sec: The white dwarf reaches the Chandrasekhar mass limit and explodes as a bright Type Ia
supernova. However, the explosion is not perfect; a fraction of the white dwarf shoots out like a shrapnel to the left. The binary system disrupts.
 
18.0 sec: The supernova explosion again, at an edge – on view. The shrapnel comes at the viewer and passes by.
 
20.0 sec: After passing by, the remnant flies off towards the disk of the Milky Way towards the spiral arm with the Solar System.
 
24.0 sec : The fast moving remnant from the solar neighborhood as it passes by the stars in our galactic arm, including the Sun. The remnant gets in the reach of our telescopes. (Copyright Sardonicus Pax)

 

A supernova — among the most powerful forces in the universe — occurs when there is a change in the core of a star. A change can occur in two different ways, with both resulting in a thermonuclear explosion.

Type Ia supernova occurs at the end of a single star’s lifetime. As the star runs out of nuclear fuel, some of its mass flows into its core. Eventually, the core is so heavy that it cannot withstand its own gravitational force. The core collapses, which results in the giant explosion of a supernova. The sun is a single star, but it does not have enough mass to become a supernova.

The second type takes place only in binary star systems. Binary stars are two stars that orbit the same point. One of the stars, a carbon-oxygen white dwarf, steals matter from its companion star. Eventually, the white dwarf accumulates too much matter. Having too much matter causes the star to explode, resulting in a supernova.

Type Ia supernovae, which are the result of the complete destruction of the star in a thermonuclear explosion, have a fairly uniform brightness that makes them useful for cosmology. The light emitted by the supernova explosion can be, for a short while at least, as bright as the whole of the Milky Way.

Recently, astronomers have discovered a related form of supernova, called Type Iax, which look like Type Ia, but are much fainter. Type Iax supernovae may be caused by the partial destruction of a white dwarf star in such an explosion. If that interpretation is correct, part of the white dwarf should survive as a leftover object.

And that leftover object is precisely what Vennes et al claim to have found.

They have identified LP 40-365 as an unusual white dwarf with a low mass, high velocity and strange composition of oxygen, sodium and magnesium  – exactly as might be expected for the leftover star from a Type Iax event. Vennes describes the white dwarf remnant his team has detected as a “compact star,” and perhaps the first of its kind in terms of the elements it contains.

The team calculate that the explosion must have occurred between five and 50 million years ago.

 

The two inset images show before-and-after images captured by NASA’s Hubble Space Telescope of Supernova 2012Z in the spiral galaxy NGC 1309, what some call a “zombie star.”. The white X at the top of the main image marks the location of the supernova in the galaxy. A supernova typically obliterates the exploding white dwarf, or dying star.  In 2014, scientists found that this faint supernova may have left behind a surviving portion of the white dwarf star.(NASA,ESA)

In an email exchange, Vennes told me that he has been studying the local white dwarf population for thirty years.

“These compact, dead stars tell us a lot about the “old” Milky Way, how stars were born and how they died,” he wrote.

“Tens of thousands of these white dwarfs have been catalogued over this past century, most of them in the last decade, but we keep an eye on outliers, objects that are out of the norm. We look for exceedingly large velocity, peculiar chemical composition or abnormal mass or radii.

Stephane Vennes, a longtime specialist in white dwarf stars at the Czech Academy of Science.

“The strange case of LP40-365 came unexpectedly, but this was a classic case of serendipity in astronomy. Out of hundreds of targets we observed at the telescope, this one was uniquely peculiar. Fortunately, theorists are very imaginative and the model we adopted to interpret the observed properties of this object were only recently published. Our research on this object was certainly inspired and directed by their theory.”

Vennes says the team was surprised to learn that the white dwarf LP40-365 is relatively bright among its peers and that similar objects did not show up in large-scale surveys such as the Sloan Digital Sky Survey.

“This fact has convinced us that many more similarly peculiar white dwarfs await discovery. We should search among fainter, more distant samples of white dwarfs,” he wrote.

And that search can be done by the European Space Agency’s Gaia astrometric space telescope, with follow-up observations at large telescopes such as the European Southern Observatory’s Very Large Telescope and the Gemini observatory in Chile.

“It is also likely that our adopted model involving a subluminous {faint} Type Ia supernova will be modified or even superseded by teams of theorists coming up with new ideas. But we remain confident that these new ideas would still involve a cataclysmic event on the scale of a supernova.”

Here is another animated version of the cataclysm described in the paper: 

An ultra-massive and compact dead star, or white dwarf, (shown as a small white star) is accreeting matter from its giant companion (the larger red star). The material escapes from the giant and forms an accretion disk around the white dwarf.
Once enough material is accreted onto the white dwarf, a violent thermonuclear runaway tears it apart and destroys the entire system. The giant star and the surviving fragment of the white dwarf are flung into space at tremendous speeds. The surviving white dwarf shrapnel hurtles towards our region of the galaxy, where its radiation is detected by ground based telescopes. (Copyright Russell Kightley)

 

A supernova burns for only a short period of time, but it can tell scientists a lot about the universe.

One kind of supernova has shown scientists that we live in an expanding universe, one that is growing at an ever increasing rate.

Scientists also have determined that supernovas play a key role in distributing elements throughout the universe. When the star explodes, it shoots elements and debris into space. Many of the elements we find here on Earth are made in the core of stars.

These elements travel on to form new stars, planets and everything else in the universe — making white dwarfs and supernovae essential to the process that ultimately led to life.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.