The Northern Lights (Part Two)

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Northern Lights at a latitude of about 70 degrees north, well within the Arctic Circle. These photos were taken about 30 miles from the town of Alta. (Lisa Braithwaite)

In my recent column about The Northern Lights, the Magnetic Field and Life,  I explored the science and the beauty of our planet’s aurora borealis, one of the great natural phenomenon we are most fortunate to see in the far North (and much less frequently in the not-quite-so-far North.)

I learned the hard way that an IPhone camera was really not up to the job;  indeed, the battery froze soon after leaving my pocket in the 10 degrees F cold.  So the column had few images from where I actually was — about a half hour outside of the Arctic Circle town of Alta.

But here now are some images taken by a generous visitor to the same faraway lodge, who was present the same time as myself.

Her name is Lisa Braithwaite and she is an avid amateur photographer and marketing manager for two popular sites in the English Lake District.  This was her first hunting trip for the Northern Lights, and she got lucky.  Even in the far northern Norway winter the lights come and go unpredictably — though you can increase your chances if you show up during a time when the sun is actively sending out solar flares.

She came with a Panasonic Lumix DMC-G5 camera and did a lot of research beforehand to increase her chances of capturing the drama should the lights appear.  Her ISOs ranged from 1,600 to 64,000, and her shutter speed from 5 to 15 seconds.  The aperture setting was 3.5.

In addition to showing some of her work, further on I describe a new NASA-led and international program, based in Norway, to study the still incompletely understood dynamics of what happens when very high energy particles from solar flares meet Earth’s atmosphere.

Partnering with the Japanese Aerospace Exploration Agency (JAXA,) the University of Oslo an other American universities, the two year project will send eleven rockets filled with instruments into the ionosphere to study phenomenon such as the auroral winds and the turbulence that can cause so much trouble to communications networks.

But first, here are some morre of Braithwaite’s images, most taken over a one hour period on a single night.

Arcs are a common feature of the lights, sometimes reaching across the sky. They form and then break up into smaller patches. (Lisa Braithwaite.)

 

The line of the Arctic Circle line can be seen a little more than half-way up the map. The Circle is the most northerly of the five major circles of latitude as shown on maps of Earth. At about 65 degrees North, it marks the northernmost point at which the noon sun is just visible on the December solstice and the southernmost point at which the midnight sun is just visible on the June solstice. (Stepmap.com)

Vast curtains of light are a common feature, often on the horizon but on good nights high up into the sky.  The lights can sometimes shimmer and dance, and can feature what appear to be vast spotlights.

 

The lights are often green — the result of interactions between high energy solar flares and oxygen.  If the lights are blue, then nitrogen is in play.  (Lisa Braithwaite)

 

At certain points in the night, large parts of the sky were lit up — leaving us turning and craning our heads to see what might be happening in different regions. (Lisa Braithwaite)

 

The light shows often start and end with green horizons.  (Lisa Braithwaite)

While the grandeur of the lights attracts an ever increasing number of adventurous lovers of natural beauty, NASA is also busy in Norway studying the forces that cause the Aurora Borealis — both for the pure science and to better understand the “space weather” that can effect astronauts in low Earth orbit as well as GPS and other communication signals.

The agency has partnered with Norwegian and Japanese colleagues, and other American scientists, in an effort to generally better understand the Earth’s polar cusp — where the planet’s magnetic field lines bend down into the atmosphere and allow particles from space to intermingle with those of Earthly origin.

Solar flares consist of electrically charged particles. They are attracted by the concentrated magnetic fields in the ionosphere around the Earth’s polar regions. This is the reason why the glorious light shows can be observed pretty much exclusively in the far north or the far south.

The two-year project will send eight rockets into space from Norway as part of collaboration of scientists known as The Grand Challenge Initiative – Cusp.

The first mission, the Auroral Zone Upwelling Rocket Experiment or AZURE, is scheduled to launch this month.  The rocket will take off from Norway’s Andøya Space Center, on an island off the far northwest coast of Norway, about 100 miles southwest of where I was near the town of Alta.

As a NASA release of March 1 described it, AZURE’s instruments will measure the atmospheric density and temperature of the polar atmosphere, and will deploy visible tracers — trimethyl aluminum (TMA) and a barium/strontium mixture, which ionize when exposed to sunlight.

Personnel from NASA’s Wallops Flight Facility in Virginia conduct payload tests for the AZURE mission at the Andøya Space Center in Norway. (NASA’s Wallops Flight Facility)

“These mixtures create colorful clouds that allow researchers to track the flow of neutral and charged particles, respectively,” the release reads. “The tracers will be released at altitudes 71 to 155 miles high and pose no hazard to residents in the region.

“By tracking the movement of these colorful clouds via ground-based photography and triangulating their moment-by-moment position in three dimensions, AZURE will provide valuable data on the vertical and horizontal flow of particles in two key regions of the ionosphere over a range of different altitudes.

“Such measurements are critical if we are to truly understand the effects of the mysterious yet beautiful aurora. The results will be key to a better understanding of the effects of auroral forcing on the atmosphere, including how and where the auroral energy is deposited.”

AZURE will focus specifically on measuring the vertical winds in these polar regions, which create a tumultuous particle soup that re-distributes the energy, momentum and chemical constituents of the atmosphere.

AZURE will study the ionosphere, the electrically charged layer of the atmosphere that acts as Earth’s interface to space, focusing specifically on the E and F regions. The E region — so-named by early radio pioneers who discovered that the region was electrically charge, and so could reflect radio waves — lies between 56 to 93 miles above Earth’s surface. The F region resides just above it, between 93 to 310 miles altitude.

The E and F regions contain free electrons that have been ejected from their atoms by the energizing input of the Sun’s rays, a process called photoionization. After nightfall, without the energizing input of the Sun to keep them separated, electrons recombine with the positively charged ions they left behind, lowering the regions’ overall electron density. The daily cycle of ionization and recombination makes the E and F regions especially turbulent and complex.

Aurora as seen from Talkeetna, Alaska, on Nov. 3, 2015. (Copyright Dora Miller)

It has been known for a century that solar flares create the fantastic displays of the Northern and Southern lights.  More recently, it has also become well known that solar flares cause problems for both satellites and navigation systems.

Despite decades of study, scientists still lack the basic knowledge required for predicting when such problems will occur. Once they understand this, it should be possible to make good space weather forecasts just like we do with our weather forecasts on Earth.

When solar storms rain down on the Earth, they cause turbulence in the ionosphere.  This turbulence is one of the major unsolved problems of classical physics and physicists are hoping that the rockets will lead to a far better understanding of the phenomenon.

“Without such an understanding of turbulence it is impossible to make the calculations needed for being able to predict severe space weather events,” said Joran Moen of the University of Oslo, and one of the project leaders. He spoke with the University of Oslo research magazine “Apollon.”

The rockets of The Grand Challenge Initiative – Cusp  mission will launch over the next two years from the Andøya and Svalbard rocket ranges in Norway. Nine of the rockets are from NASA, one from JAXA and one building built the at the University of Norway.

One particular “sounding” will be made with the launch of four rockets at once, an unusual and complex procedure.

Those involved say this will be among the most ambitious attempts ever using rockets for research purposes.

“We will try to launch four of the rockets at the same time. This has never been done before. It is a historic venture,” said Moen.

Yoshifumi Saito of JAXA further explained that “the four parallel rockets are important for us.  By using them we can obtain much better scientific results than would have been the case if we had just launched one rocket at a time.”

Important and compelling science.  And think of how many times the scientists will be able to experience the glories of the Northern Lights show.

 

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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.

The Northern Lights, the Magnetic Field and Life

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Northern Lights over a frozen lake in Northern Norway, inside the Arctic Circle near Alta. The displays can go on for hours, or can disappear for days or weeks. It all depends on solar flares. (Ongajok.no)

May I please invite you to join me in the presence of one of the great natural phenomena and spectacles of our world.

Not only is it enthralling to witness and scientifically crucial, but it’s quite emotionally moving as well.

Why? Because what’s before me is a physical manifestation of one of the primary, but generally invisible, features of Earth that make life possible. It’s mostly seen in the far northern and far southern climes, but the force is everywhere and it protects our atmosphere and us from the parched fate of a planet like Mars.

I’m speaking, of course, of the northern lights, the Aurora Borealis, and the planet’s magnetic fields that help turn on the lights.

My vantage point is the far northern tip of Norway, inside the Arctic Circle. It’s stingingly cold in the silent woods, frozen still for the long, dark winter, and it’s always an unpredictable gift when the lights show up.

But they‘re out tonight, dancing in bright green and sometimes gold-tinged arches and spotlights and twirling pinwheels across the northerly sky. Sometimes the horizon glows green, sometimes the whole sky fills with vivid green streaks.

It can all seem quite other-worldly. But the lights, of course, are entirely the result of natural forces.

 

Northern Lights over north western Norway. Most of the lights are green from collisions with oxygen, but some are purple from nitrogen. © Copyright George Karbus Photography

It has been known for some time that the lights are caused by reactions between the high-energy particles of solar flares colliding in the upper regions of our atmosphere and then descending along the lines of the planet’s magnetic fields. Green lights tell of oxygen being struck at a certain altitude, red or blue of nitrogen.

But the patterns — sometimes broad, sometimes spectral, sometimes curled and sometimes columnar — are the result of the magnetic field that surrounds the planet. The energy travels along the many lines of that field, and lights them up to make our magnetic blanket visible.

Such a protective magnetic field is viewed as essential for life on a planet, be it in our solar system or beyond.

But a magnetic field does not a habitable planet make. Mercury has a weak magnetic field and is certainly not habitable. Mars also once had a strong magnetic field and still has some remnants on its surface. But it fell apart early in the planet’s life, and that may well have put a halt to the emergence or evolution of living things on the otherwise habitable planet.

I will return to some of the features of the northern lights and the magnetism is makes visible, but this is also an opportunity to explore the role of magnetism in biology itself.

This was a quasi-science for some time, but more recently it has been established that migrating birds and fish use magnetic sensors (in their beaks or noses, perhaps) to navigate northerly and southward paths.

Graphic from Science Magazine.

 

But did you know that bacteria, insects and mammals of all sorts appear to have magnetic compasses as well?   They can read the magnetism in the air, or can read it in the rocks (as in the case of some sea turtles.) A promising line of study, pioneered by scientists including geobiologist Joseph Kirschvink of the California Institute of Technology (Caltech) and the Earth-Life Science Institute (ELSI) in Tokyo, is even studying potentially remnant magnetic senses in humans.

“There no doubt now that magnetic receptors are present in many, many species, and those that don’t have it probably lost it because it wasn’t useful to them,” he told me. “But there’s good reason to say that the magnetic sense was most likely one of the earliest on Earth.”

But how does it work for animals? How do they receive the magnetic signals? This is a question of substantial study and debate.

One theory states that creatures use the iron mineral magnetite — that they can produce and consume – to pick up the magnetic signals. These miniature compass needles sit within receptor cells, either near a creature’s nose or in the inner ear.

Joseph Kirschvink, a geobiologist with Caltech and ELSI (the Earth-Life Science Institute in Tokyo) has been studying for decades the ways in which creatures from bacteria to humans use magnetic forces in their lives. (Caltech)

Another posits that magnetic fields trigger quantum chemical reactions in proteins called cryptochromes, which have been found in the retina. But no one has determined how they might send signals and information to the brain.

Kirschvink was part of a team that demonstrated bacteria’s use of Earth’s magnetic field back to the Archean era, 3 to 3.5 billion years ago.   “My guess is that magnetism has had a major influence on the biosphere since then, via the biological ability to make magnetic materials.”

He said that when the sun is particularly angry and active, the geomagnetic storms that occur around the planet seem to interfere with these magnetic responses and that animals don’t navigate as well.

Kirschvink sees magnetism as a possibly important force in the origin of life. Magnetite that is lined up like beads on a chain has been detected in bacteria, and he says it may have provided an evolutionary pathway for structure that allowed for the rise of eukaryotes — organisms with complex cells, or a single cell with a complex structures.

Kirschvink and his team are in the midst of a significant study of the effects of geomagnetism on humans, and the pathways through which that magnetism might be used.

That’s rather a long way from some of the early biomagnetism discoveries, which involved the chiton.  A mollusk relative of the snail and the limpet, the chiton holds on to rocks in the shallow water and uses its magnetite-covered teeth to scrape algae from rocks.  The teeth are on a tongue-like feature called the radula and those teeth are capped with so much magnetite that a magnet can pick up the foot-long gumboot chiton, the largest of the species.

The underside of a gumboot chiton, with its teeth covered with magnetite, can be lifted up with a magnet.

Back at most northern and southerly regions of the planet, where the magnetic field lines are most concentrated, the lights put on their displays for ever larger audiences of people who want to experience their presence.

We had part of one night of almost full sky action, with long arches, curves large and small, waves, spotlights , shimmers and curtains.  It had the feel of a spectacular fireworks display, but magnified in its glory and power and, of course, entirely natural.  (I hope to post images taken by others that night which, alas, were not captured by my camera because the battery froze in the 10 degree cold.)

Our grand night was one of the special ones when the colors (almost all greens, but some reds too) were so bright that their shapes and movements were easy to see with the naked eye.

Good cameras (especially those with batteries that don’t freeze) see and capture a much broader range of the northern light presence.  The horizon, for instance, can appear just slightly green to the naked eye, but will look quite brightly green in an image.

Thanks to the National Oceanic and Atmospheric Administration, the National Weather Service and NASA, forecasting when and where the lights are likely to be be active in the northern and southern (the Aurora Australis) polar regions.

This forecasting of space weather revolves around the the eruption of solar flares.  The high-energy particles they send out collide with electrons in our upper atmosphere accelerate and follow the Earth’s magnetic fields down to the polar regions.

Models based on measuring solar flares, or coronal mass ejections, coming from sunspots that rotate and face Earth every 27 or 28 days.  Summer months in the northern hemisphere often make the sky too light for the lights to be seen, so the long winter nights are generally the best time to see them.  But they do appear in summer, too.  (NOAA)

In these collisions, the energy of the electrons is transferred to the oxygen and nitrogen and other elements in the atmosphere, in the process exciting the atoms and molecules to higher energy states. When they relax back down to lower energy states, they release their energy in the form of light. This is similar to how a neon light works.

The aurora typically forms 60 to 400 miles above Earth’s surface.

All this is possible because of our magnetic field, which scientists theorize was created and is sustained by interactions between super-hot liquid iron in the outer core of the Earth’s center and the rotation of the planet.  The flowing or convection of liquid metal generates electric currents and the rotation of Earth causes these electric currents to form a magnetic field which extends around the planet.

If the magnetic field wasn’t present those highly charged particles coming from the sun, the ones that set into motion the processes that produce the Northern and Southern Lights, would instead gradually strip the atmosphere of the molecules needed for life.

This intimate relationship between the magnetic field and life led to me ask Kirschvink, who has been studying that connection for decades, if he had seen the northern or southern lights.

No, he said, he’d never had the chance.  But if ever in the presence of the lights, he said he know exactly what he would do:  take out his equipment and start taking measurements and pushing his science forward.

Northern Lights in northern Norway, near Alta.  Sometimes they dance for minutes, sometimes for hours, but often they never come at all.  It all depends on the rotation of the sun; if and when it may be shooting out high-energy solar flares. (Wiki Commons)
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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.

To Understand Habitability, We Need to Return to Venus

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This column was written by my colleague, Elizabeth Tasker.  Based in Tokyo, she is a scientist and communicator at the Japanese Space Agency JAXA and the Earth-Life Science Institute (ELSI).  Her book, “The Planet Factory,” was published last fall.


This image shows the night side of Venus in thermal infrared. It is a false-color image using data from the Japanese spacecraft Akatsuki’s IR2 camera in two wavelengths, 1.74 and 2.26 microns. Darker regions denote thicker clouds, but changes in color can also denote differences in cloud particle size or composition from place to place.  JAXA / ISAS / DARTS / Damia Bouic

“You can feel what it’s like on Venus here on Earth,” said Kevin McGouldrick from the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder. “Heat a hot plate until it glows red, place your palm on its surface and then run over that hand with a truck.”

The surface of Venus is a hellish place. Suffocated by a thick atmosphere, pressure on the Venusian surface is 92 times greater than on the surface of Earth. Temperatures sit at a staggering 863°F (462°C), which is sufficient to melt lead.

The longest a spacecraft has survived in these conditions is a mere 127 minutes; a record set by the Russian Venera 13 mission over 35 years ago.

As the brightest planet in the night sky, Venus allured ancient astronomers into naming the world after the Roman mythological goddess of love and beauty. This now seems an ironic choice, but the contrast between distant observation and surface conditions produces an apt juxtaposition for exoplanets.

The comparison has led to an article in Nature Geoscience by McGouldrick and a nine author white paper advising on astrobiology strategy for the National Science Foundation. The conclusion of both publications echoes the irony of Venus’s name: we need to return to the inferno of Venus to understand habitable worlds.

 

A portion of western Eistla Regio is displayed in this three-dimensional perspective view of the surface of Venus. Synthetic aperture radar data from the spacecraft Magellan is combined with radar altimetry to develop a three-dimensional map of the surface. Rays cast in a computer intersect the surface to create a three-dimensional perspective view.  The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image, a frame from a video released in 1991, was produced at NASA’s JPL Multimission Image Processing Laboratory.

In the last 25 years, scientists have discovered over 3,500 extrasolar planets. The vast majority of these worlds have not been imaged directly, but are detected by tiny influences on their host star. These observations provide a measurement of the planet’s size and the average energy received from the star, but no details of the conditions at the planet surface. This leaves modern astronomers as blind to exoplanets as the ancient Romans were to the worlds of our solar system.

While we cannot visit the surface of exoplanets, our knowledge may be about to take a major leap forward. New instruments such as NASA’s James Webb Space Telescope (launch date 2019) and ESA’s Ariel mission (launch 2026) are aiming to detect the atmospheres of these distant worlds. The enveloping gases are a product of the planet’s geology, chemistry and biology, producing a direct indication of what is occurring on the surface.

However, this signature is hard to measure for terrestrial worlds with thin atmospheres, requiring a large number of precious observing hours. This means we need to select our telescope targets carefully. An ideal choice would be a planet writhing with geological and biological activity that is imprinting its presence in the atmosphere.

In short, what we want is an exo-Earth. What we don’t want is an exo-Venus.

Surface photographs from the former Soviet Union’s Venera 13 spacecraft, which touched down in March 1982. Ten probes from the Venera series successfully landed on Venus and transmitted data from the surface of the planet between 1961 and 1984. In addition, thirteen Venera probes successfully transmitted data from the atmosphere of Venus.

At first glance, a tantalizingly simple way to distinguish these two planets is the circumstellar habitable zone. Broadly defined, this is the region around a star where the radiation levels are right to support liquid water on a planet’s surface. At the inner edge of the habitable zone, water evaporates and is rapidly lost from the planet in a process known as ‘runaway greenhouse’. At the outer edge, carbon dioxide condenses into clouds and is unable to trap sufficient heat to prevent global freezing.

With a thick atmosphere lacking in water, Venus shows signs of having undergone a runaway greenhouse phenomenon that would seem to support the habitable zone edges. But digging a little deeper reveals more complex story. The habitable zone edges are traditionally calculated via climate models for the Earth. Yet, there is evidence that Venus was never that similar to the home planet we know.

While the Earth’s crust is broken into plates, Venus is thought to have a ‘stagnant lid’; a non-mobile crust that does not cycle material and nutrients up from the planet’s interior. Possibly linked with that —or maybe not— Venus has no magnetic field and would likely have suffered a similar fate to Mars and lost most of its atmosphere if it did not have such a thick reservoir of gases. There are almost certainly other differences; we don’t know because we haven’t been back to the Venusian surface since the 1980s.

What this means is that the path that led Venus to be an unimaginable inferno likely started a long time before a runaway greenhouse could occur.

If the deviation from Earth were initially driven by geodynamics, formation or other non-climate differences (such as the failure to form crustal plates, or poor internal heat circulation preventing a magnetic field) then the boundary between Earth and Venus is likely unrelated to the climate-based habitable zone. Without understanding the history of this second Earth-sized planet in our own system, we have no hope of differentiating between a Venus or Earth around another star.

A topographic map of Venus, with sinusoidal projection, based on data from the Magellan spacecraft, which was one of the few missions launched from the space shuttle.  It left for Venus in 1989 and mapped the planet until 1994.  (NASA)

But is this concern unnecessary? While an exo-Venus would not be an interesting place to hunt for signatures of life, we might learn about the formation of our two worlds by exploring the atmosphere of similar planets around other stars.

And this is where we hit a second problem; we don’t understand the atmosphere of Venus.

Models predict that planets that have undergone a runaway greenhouse should have an oxygen rich atmosphere. This is from evaporated water molecules that are broken apart by the ultraviolet radiation from the Sun, causing the constituent hydrogen atoms to escape the planet’s gravity while the heavier oxygen is left behind.  Venus’s atmosphere isn’t oxygen rich. It’s full of carbon dioxide and clouds of sulphuric acid.

This leaves us trying to understand the distant signature of alien atmospheres without a good comprehension of the examples we have in our own Solar System.

These arguments present a compelling case for Venus. Yet although three out of twelve proposals for NASA’s New Frontiers Program were for Venus missions, none were selected as finalists last December. The same was true for the last call for the Discovery Program; two out of five finalists for this lower cost mission category were for Venus, but neither were selected despite Discovery proposals being typically more focussed on the inner Solar System.

Kevin McGouldrick of the University of Colorado, Boulder, says the primary focus of his research is the nature and evolution of the clouds of Venus. Some 35 to 55 miles above the surface of Venus,  temperatures and pressures resemble those at the surface of the Earth.

Is there a reluctance to go to Venus?

Undoubtedly, planet surface conditions that can melt a spacecraft curbs enthusiasm. The insulation required to protect a probe on the Venusian surface or conduct a short mission will drive costs skyward and may seem a poor return compared to other projects.

Missions to study the Venusian atmosphere would be substantially less risky. The only mission currently operating around Venus is Japan’s Akatsuki orbiter, which last year returned data suggesting mountainous terrain on Venus was sufficient to drive waves through the huge weather system.

In his Nature Geoscience article, McGouldrick proposes that detailed monitoring of Venus’s atmosphere is needed to understand the planet’s history. “To find out why Venus is how it is now, we need to know how it used to be,” he pointed out.

This information could be found in the abundances and isotopes (different variations of the same element) of the noble gases on Venus. These unreactive elements are acquired during planet formation, so changes in their quantities indicate losses in Venus’s past of strippable quantities such as atmosphere and water. Comparison with Earth can also indicate if the two planets formed from similar materials, or if part of the dichotomy between these Earth-sized worlds can be laid at the door of compositional differences.

But another orbiter loses out on basic appeal. NASA planetary exploration typically follows the pattern of fly-by spacecraft, orbiters, landers and rovers and then missions to return samples to Earth. Mars exploration is following this list, with the planned Mars 2020 mission collecting samples for possible later collection. Missions to Europa and Mercury are doing the same, albeit at an earlier stage.

But the hellish surface conditions of Venus make this pattern difficult, and the prospect of repeating the orbiter step with better instruments is significantly less enticing.

The solution might be a combined orbiter and lander mission, with data from the orbiter mitigating the risk associated with the lander. Alternatively, an aeroplane or balloon that travels through the upper parts of the Venusian atmosphere might combine originality with data that cannot be achieved in orbit. Designs like these have been proposed for a Russia-led mission with a contribution from NASA, known as Venera-D, but funding remains uncertain.


This image of the equatorial region of Venus taken by the Japanese Akatsuki probe provides striking detail of the equatorial, tropical, and extra-tropical clouds of the planet. Color changes indicate local variations in the amounts of a little-understood ultraviolet absorber and sulfur dioxide in the atmosphere. JAXA / ISAS / DARTS / Damia Bouic

While a Venus mission did not make into the finalists for the New Frontiers program, funding was given to develop a camera that could measure the mineralogy and composition of Venus’s rocks. This demonstrates a continual interest by mission experts in Venus, but publications by the community suggest this needs to be higher up the priority list.

The bottom line is that visiting our neighbor may present one of the biggest challenges in the Solar System. But exoplanet research may be lost without it.

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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.

False Positives, False Negatives; The World of Distant Biosignatures Attracts and Confounds

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This artist’s illustration shows two Earth-sized planets, TRAPPIST-1b and TRAPPIST-1c, passing in front of their parent red dwarf star, which is much smaller and cooler than our sun. NASA’s Hubble Space Telescope looked for signs of atmospheres around these planets. (NASA/ESA/STScI/J. de Wit, MIT)

What observations, or groups of observations, would tell exoplanet scientists that life might be present on a particular distant planet?

The most often discussed biosignature is oxygen, the product of life on Earth.  But while oxygen remains central to the search for biosignatures afar, there are some serious problems with relying on that molecule.

It can, for one, be produced without biology, although on Earth biology is the major source.  Conditions on other planets, however, might be different, producing lots of oxygen without life.

And then there’s the troubling reality that for most of the time there has been life on Earth, there would not have been enough oxygen produced to register as a biosignature.  So oxygen brings with it the danger of both a false positive and a false negative.

Wading through the long list of potential other biosignatures is rather like walking along a very wet path and having your boots regularly pulled off as they get captured by the mud.  Many possibilities can be put forward, but all seem to contain absolutely confounding problems.

With this reality in mind, a group of several dozen very interdisciplinary scientists came together more than a year ago in an effort to catalogue the many possible biosignatures that have been put forward and then to describe the pros and the cons of each.

“We believe this kind of effort is essential and needs to be done now,” said Edward Schwieterman, an astronomy and astrobiology researcher at the University of California, Riverside (UCR).

“Not because we have the technology now to identify these possible biosignatures light years away, but because the space and ground-based telescopes of the future need to be designed so they can identify them. ”

“It’s part of what may turn out to be a very long road to learning whether or not we are alone in the universe”.

 

Artistic representations of some of the exoplanets detected so far with the greatest potential to support liquid surface water, based on their size and orbit.  All of them are larger than Earth and their composition and habitability remains unclear. They are ranked here from closest to farthest from Earth.  Mars, Jupiter, Neptune an Earth are shown for scale on the right. (Planetary Habitability Laboratory, managed by the University of Puerto Rico at Arecibo.)

The known and inferred population of exoplanets — even small rocky exoplanets — is now so vast that it’s tempting to assume that some support life and that some day we’ll find it.  After all,  those billions of planets are composed of same basic chemical elements as Earth and are subject to the same laws of physics.

That assumption of life widespread in the galaxies may well turn out to be on target.  But assuming this result, and proving or calculating a high probability of finding extraterrestrial life, are light years apart.

The timing of this major community effort is hardly accidental.  There is a National Academy of Sciences effort underway to review progress in the science of reading possible biosignatures from distant worlds, something that I wrote about recently.

Edward Schwieterman, spent six years at the University of Washington’s Virtual Planetary Laboratory.  He now works with the NASA Astrobiology Institute Alternative Earths team UCR.

The results from the NAS effort will in term flow into the official NAS decadal study that will follow and will recommend to Congress priorities for the next ten or twenty years.  In addition, two NASA-ordered science and technology definition teams are currently working on architectures for two potential major NASA missions for the 2030s — HabEx (the Habitable Exoplanet Imaging Mission) and Luvoir (the Large Ultraviolet/Optical/Infrared Surveyor.)

The two mission proposals, which are competing with several others, would provide the best opportunity by far to determine whether life exists on other distant planets.

With these formal planning and prioritizing efforts as a backdrop, NASA’s Nexus for Exoplanet System Science (NExSS) called for a biosignatures workshop in the fall of 2016 and brought together scientists from many disciplines to wrestle with the subject.  The effort led to the white paper submitted to NAS and will result in and will result in the publication of series of five detailed papers in the journal Astrobiology this spring.” The overview paper with Schwieterman as first author, which has already been made available to the community for peer review, is expected to lead off the package.

So what did they find?  First off, that Earth has to be their guide.

“Life on Earth, through its gaseous products and reflectance and scattering properties, has left its fingerprint on the spectrum of our planet,” the paper reads. “Aided by the universality of the laws of physics and chemistry, we turn to Earth’s biosphere, both in the present and through geologic time, for analog signatures that will aid in the search for life elsewhere.

Considering the insights gained from modern and ancient Earth, and the broader array of hypothetical exoplanet possibilities, we have compiled a state-of-the-art overview of our current understanding of potential exoplanet biosignatures including gaseous, surface, and temporal biosignatures.”

In other words, potential biosignatures in the atmosphere, on the ground, and that become apparent over time.  We’ll start with the temporal:

These vegetation maps were generated from MODIS/Terra measurements of the Normalized Difference Vegetation Index (NDVI). Significant seasonal variations in the NDVI are apparent between northern hemisphere summer  and winter. (Reto Stockli, NASA Earth Observatory Group, using data from the MODIS Land Science Team.)

Vegetation is probably clearest example of how change-over-time can be a biosignature.  As these maps show and we all know, different parts of the Earth have different seasonal colorations.  Detecting exoplanetary change of this sort would be a potentially strong signal, though it could also have some non-biological explanations.

If there is any kind of atmospheric chemical corroboration, then the time signal would be a strong one.  That corroboration could come in seasonal modulations of biologically important gases such as CO2 or O2.  Changes in cloud cover and the periodic presence of volcanic gases can also be useful markers over time.

Plant pigments themselves which have been proposed as a surface biosignature.  Observed in the near infrared portion of the electromagnetic spectrum, the pigment chlorophyll — the central player in the process of photosynthesis — shows a sharp increase in reflectance at a particular wavelength.  This abrupt change is called the “red edge,” and is a measurement known to exist only which chlorophyll engaged in photosynthesis.

So the “red edge,” or parallel dropoffs in reflectance of other pigments on other planets, is another possible biosignature in the mix.

And then there is “glint,” reflections from exoplanets that come from light hitting water.

True-color image from a model (left) compared to a view of Earth from the Earth and Moon Viewer (http://www.fourmilab.ch/cgi-bin/Earth/). A glint spot in the Indian Ocean can be clearly seen in the model image.

Since biosignature science essentially requires the presence of H2O on a planet, the clear detection of an ocean is part of the process of assembling signatures of potential life.  Just as detecting oxygen in the atmosphere is important, so too is detecting unmistakable surface water.

But for reasons of both science and detectability, the chemical make-up exoplanet atmospheres is where much biosignature work is being done.  The compounds of interest include (but are not limited to) ozone, methane, nitrous oxide, sulfur gases, methyl chloride and less specific atmospheric hazes.  All are, or have been, associated with life on Earth, and potentially on other planets and moons as well.

The Schwieterman et al review looks at all these compounds and reports on the findings of researchers who have studied them as possible biosignatures.  As a sign of how broadly they cast their net, the citations alone of published biosignature papers number more than 300.

(Sara Seager and William Bains of MIT, both specialists in exoplanet atmospheres, have been compiling a separate and much broader list of potential biosignatures, even many produced in very small quantities on Earth.  Bains is a co-author on one of the five biosignature papers for the journal Astrobiology.)

All this work, Schwieterman said, will pay off significantly over time.

“If our goal is to constrain the search for life in our solar neighborhood, we need to know as much as we possibly can so the observatories have the necessary capabilities.  We could possibly save hundreds of millions or billions of dollars by constraining the possibilities.”

“The strength of this compilation is the full body of knowledge, putting together what we know in a broad and fast-developing field,” Schwieterman said. ”

He said that there’s such a broad range of possible biosignatures, and so many conditions where some might be more or less probable, that’s it’s essential to categorize and prioritize the information that has been collected (and will be collected in the future.)

“We have a lot of observations recorded here, but they will all have their ambiguities,” he said.  “Our goal as scientists will be to take what we know and work to reduce those ambiguities. It’s an enormous task.”

 

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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.

Putting Together a Community Strategy To Search for Extraterrestrial Life

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I regret that the formatting of this column was askew earlier; I hope it didn’t make reading too difficult.  But now those problems are fixed.

The scientific search underway for life beyond Earth requires input from many disciplines and fields. Strategies forward have to hear and take in what scientists in those many fields have to say. (NASA)

Behind the front page space science discoveries that tell us about the intricacies and wonders of our world are generally years of technical and intellectual development, years of planning and refining, years of problem-defining and problem-solving.  And before all this, there also years of brainstorming, analysis and strategizing about which science goals should have the highest priorities and which might be most attainable.

That latter process is underway now in regarding the search for life in the solar system and beyond, with numerous teams of scientists tackling specific areas of interest and concern and turning their group discussions into white papers.  In this case, the white papers will then go on to the National Academy of Sciences for a blue-ribbon panel review and ultimately recommendations on which subjects are exciting and mature enough for inclusion in a decadal survey and possible funding.

This is a generally little-known part of the process that results in discoveries, but scientists certainly understand how they are essential.  That’s why hundreds of scientists contribute their ideas and time — often unpaid — to help put together these foundational documents.

With its call for extraterrestrial habitability white papers, the NAS got more than 20 diverse and often deeply thought out offerings.  The papers will be studied now by an ad hoc, blue ribbon committee of scientists selected by the NAS, which will have the first of two public meetings in Irvine, Calif. on Jan. 16-18.

Shawn Domagal-Goldman, a leader of many NASA study projects and a astrobiologist at NASA’s Goddard Space Fight Center. (NASA)

Then their recommendations go up further to the decadal survey teams that will set formal NASA priorities for the field of astronomy and astrophysics and planetary science.  This community-based process that has worked well for many scientific disciplines since they began in the late 1950s.

I’m particularly familiar with two of these white paper processes — one produced at the Earth-Life Science Institute (ELSI) in Tokyo and the other with NASA’s Nexus for Exoplanet System Science (NExSS.)  What they have to say is most interesting.

This is what Shawn Domagal-Goldman, an astrobiologist at the Goddard Space Flight Center, had to say about their effort, which began 16 months ago with a workshop in Seattle:

Chaitanya Giri, a research scientist and the Earth-Life Science Institute in Tokyo. (Nerissa Escanlar)

“This is an ‘all-hands-on-deck’ problem, and we held a workshop to start drawing a wide variety of scientists to the problem. Once we did, the group gave itself an ambitious goal – to quantify an assessment of whether or not an exoplanet has life, based on remote observations of that world.

“Doing that will take years of collaboration of scientists like the ones at the meeting, from diverse backgrounds and diverse experiences.”

Chaitanya Giri, a research scientist at ELSI with a background in organic planetary chemistry and organic cosmochemistry, said that his work on the European Rosetta mission to a comet convinced him that it is essential to “develop technological capacities to explore habitable niches on various planetary bodies and find unambiguous signatures of life, if present.”  There is some debate about the organic molecules — the chemical building blocks of life — identified by Rosetta.

“Over the years there have been scattered attempts at building such instruments, but a coherent collaborative network was missing,” Giri said. “This necessity inspired me to put on this workshop,” which led to the white paper.

We’ll discuss the conclusions of the papers, but first at little about the decadal surveys:

NASA Decada:

Here are the instruction from the NAS to potential white paper teams working on life beyond Earth projects and issues:

  • Identify promising key research goals in the field of the search for signs of life in which progress is likely in the next 20 years.
  • Identify key technological challenges in astrobiology as they pertain to the search for life in the solar system and extrasolar planetary systems.
  • Identify key scientific questions in astrobiology as they pertain to the search for life in the solar system and extrasolar planetary systems
  • Discuss scientific advances that can be addressed by U.S. and international space missions and relevant ground-based activities in operation or funded and in development
  • Discuss how to expand partnerships (interagency, international and public/private) in furthering the study of life’s origin, evolution, distribution, and future in the universe

Quite a wide net, from specific issues to much broader ones.  But the teams submitting their papers are not expected to address all the issues, but only one or perhaps a related second.

The papers range from a SETI Institute call for a program to increase the use of artificial intelligence and machine learning to address a range of astrobiology issues; to tempting possibilities offered by teams already in the running for future missions to Europa or Enceladus or elsewhere; to recommendations from the Planetary Science Institute about studying and searching for microbialites, living carbonate rock structures once common on Earth and possibly on Mars as well.

 

Proposed White Paper Subjects

Saturn’s moon Enceladus and plume of water vapor flowing out from its South Pole. (NASA)

 

Microbialites are fresh water versions of the organic and carbonate structures called stromatolites — which are among the oldest signs of life detected on Earth.

 

The white paper from ELSI focuses how to improve and discover technology that can detect potential life on other planets and moons. It calls for an increasingly international approach to that costly and specialized effort.

The paper from Giri et al begins with a disquieting conclusion that only “lately, scattered efforts are being undertaken towards the R&D of the novel and as-yet space unproven ‘life-detection’ technologies capable of obtaining unambiguous evidence of extraterrestrial life, even if it is significantly different from {Earth} life. As the suite of space-proven payloads improves in breadth and sensitivity, this is an apt time to examine the progress and future of life-detection technologies.”

The paper points to one discovery in particular as indicative of what the team feels is necessary — an ability to search for life in regions theoretically devoid of life and therefore requiring novel detection
techniques or probes.

“For example,” they write, “air sampling in Earth’s stratosphere with a novel scientific cryogenic payload has led to the isolation and identification of several new species of bacteria; this was an innovative technique analyzing a region of the atmosphere that was initially believed to be devoid of life.”

Other technologies they see as promising and needing further development are high-sensitivity fluorescence microscopy techniques that may be able to detect extraterrestrial organic compounds with catalytic activity surrounded by membranes, i.e., extraterrestrial cells.  In addition, they support on-going and NASA-funded work on genetic samplers that could go to Mars and — if present — actually identify nucleic acid-based life.

“With back-to-back missions under development and proposed by various space agencies to the potentially habitable Mars, Enceladus, Titan, and Europa, this is a right time for a detailed envisioning of the technologies needed for detection of life,” Giri said in an e-mail.

 

Yellowknife Bay on Mars, where the rover Curiosity first found conditions that were habitable to life. The rover subsequently found many more habitable spots, but no existing or fossil microbial life so far. (NASA)

The NExSS white paper on potentially detectable biosignatures from distant exoplanets– one of four submitted by the group– is an especially ambitious one.  The NASA-sponsored effort brought in many top scientists working in the field of biosignatures, and in the past year has already resulted in the publication or submission of five major science papers in addition to the white paper.

In keeping with the interdisciplinary mission of NExSS, the paper brought in people from many fields and ultimately advocates for a Bayesian approach to exoplanet life detection (named after 18th century statistician and philosopher Thomas Bayes. )

In most basic terms, the Bayes approach describes the probability of an event based on prior knowledge of conditions that might be related to the event. A simple example:  Runners A and B have competed four times, and runner A won three times.  So the probability of A winner is high, right?  But what if the two competed twice on a rainy track and each won one race.  If the forecast for the day of the next race is rain, the probability of who will be the winner would change.

This  approach not only embraces probability as an essential way forward, but it is especially useful in terms of weighing probabilities involving many measurements and fields.   Because the factors involved in finding a biosignature are so complex and potentially confounding, they argue, the field has to think in terms of the probability that a number of biosignatures together suggest the presence of life, rather than a 100 percent certain detection (although that may some day be possible.)

Nancy Kiang of the Goddard Institute for Space Studies in New York, explores (among other subjects) the possibility of using photosynthetic pigments as biosignatures on exoplanets.

Nancy Kiang of the Goddard Institute for Space Studies in New York, explores (among other subjects) the possibility of using photosynthetic pigments as biosignatures on exoplanets.

 

Both Domagal-Goldman and collaborator Nancy Kiang of NASA’s Goddard Institute for Space Studies are eager to adopt climate modeling and it’s ability to use known characteristics of divergent sub-fields to put together a big picture. (Those two, along with Niki Parenteau of NASA Ames Research Center led the NExSS effort.)

“For instance,” Kiang said, “the general circulation model (GCM) at GISS simulates the global circulation patterns of a planet’s wind, heat, moisture, and gases, providing statistical behaviors of the simulated climate.”  She sees a similar possibility with exoplanets and biosignatures.

 

Such a computer model can take in data from different fields and come up with some probabilities.  The model “might tell us that a planet is habitable over a certain percent of its surface,” she said.

“A geochemist or planetary formation person might then tell us that if certain chemistry exists on that planet, it has good potential for prebiotic compounds to form. A biologist and geologist might tell us that certain surface signatures on the planet are plausible for either life or mineral background.” That’s not a robust biosignature, but the probability that it could be life is not zero, depending on origin of the signature.

“These different forms of information can be integrated into a Bayesian analysis to tell us the likelihood of life on the planet,” she wrote.

One arm of the NExSS team is already using the tools of climate modeling to predict how particular conditions on exoplanets would play out under different circumstances.

 

This is a plot of what the sea ice distribution could look like on a synchronously rotating ocean world. The star is off to the right, blue is where there is open ocean, and white is where there is sea ice.  (NASA/GISS/Anthony Del Genio)

I will return to the NExSS biosignatures white paper later, since it is so rich with cutting edge thinking about this upcoming stage in space science.  But I do want to include one specific recommendation made by the group, which calls itself the Exoplanet Biosignatures Workshop Without Walls (EBWWW).

What they say is necessary now is for more biologists to join the search for extraterrestrial life.

“The EBWWW revealed that the search for exoplanet life is still largely driven by astronomers and planetary scientists, and that this field requires more input from origins of life researchers and biologists to advance a process-based understanding for planetary biosignatures.

“This includes assessing the {already assessed probability} that a planet may have life, or a life process evolved for a given planet’s environment. These advances will require fundamental research into the origins and processes of life, in particular for environments that vary from modern Earth’s. Thus, collaboration between origins of life researchers, biologists, and planetary scientists is critical to defining research questions around environmental context.”

The recommendation, it seems to me, illustrates both the youth and a maturing of the field.

 

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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.