15,000 Galaxies in One Image

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Astronomers have just assembled one of the most comprehensive portraits yet of the universe’s evolutionary history, based on a broad spectrum of observations by the Hubble Space Telescope and other space and ground-based telescopes.  Each of the approximately 15,000 specks and spirals are galaxies, widely distributed in time and space. (NASA, ESA, P. Oesch of the University of Geneva, and M. Montes of the University of New South Wales)

Here’s an image to fire your imagination: Fifteen thousand galaxies in one picture — sources of light detectable today that were generated as much as 11 billion years ago.

Of those 15,000 galaxies, some 12,000 are inferred to be in the process of forming stars.  That’s hardly surprising because the period around 11 billions years ago has been determined to be the prime star-forming period in the history of the universe.  That means for the oldest galaxies in the image, we’re seeing light that left its galaxy but three billion years after the Big Bang.

This photo mosaic, put together from images taken by the Hubble Space Telescope and other space and ground-based telescopes, does not capture the earliest galaxies detected. That designation belongs to a galaxy found in 2016 that was 420 million years old at the time it sent out the photons just collected. (Photo below.)

Nor is it quite as visually dramatic as the iconic Ultra Deep Field image produced by NASA in 2014. (Photo below as well.)

But this image is one of the most comprehensive yet of the history of the evolution of the universe, presenting galaxy light coming to us over a timeline up to those 11 billion years.  The image was released last week by NASA and supports an earlier paper in The Astrophysical Journal by Pascal Oesch of Geneva University and a large team of others.

And it shows, yet again, the incomprehensible vastness of the forest in which we are a tiny leaf.

Some people apparently find our physical insignificance in the universe to be unsettling.  I find it mind-opening and thrilling — that we now have the capability to not only speculate about our place in this enormity, but to begin to understand it as well.

The Ultra-Deep field composite, which contains approximately 10,000 galaxies.  The images were collected over a nine-year period.  {NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)} 

For those unsettled by the first image, here is the 2014 Ultra Deep Field image, which is 1/14 times the area of the newest image.  More of the shapes in this photo look to our eyes like they could be galaxies, but those in the first image are essentially the same.

In both images, astronomers used the ultraviolet capabilities of the Hubble, which is now in its 28th year of operation.

Because Earth’s atmosphere filters out much ultraviolet light, the space-based Hubble has a huge advantage because it can avoid that diminishing of ultraviolet light and provide the most sensitive ultraviolet observations possible.

That capability, combined with infrared and visible-light data from Hubble and other space and ground-based telescopes, allows astronomers to assemble these ultra deep space images and to gain a better understanding of how nearby galaxies grew from small clumps of hot, young stars long ago.

The light from distant star-forming regions in remote galaxies started out as ultraviolet. However, the expansion of the universe has shifted the light into infrared wavelengths.

These images, then,  straddle the gap between the very distant galaxies, which can only be viewed in infrared light, and closer galaxies which can be seen across a broad spectrum of wavelengths.

The farthest away galaxy discovered so far is called GN-z11 and is seen now as it was 13.4 billion years in the past.  That’s  just 400 million years after the Big Bang.

GN-z11 is surprisingly bright infant galaxy located in the direction of the constellation of Ursa Major. Thus NASA video explains much more:

The farthest away galaxy ever detected — GN-z11. {NASA, ESA, P. Oesch (Yale University, Geneva University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz)} 

 

Galaxy formation chronology, showing GN-z11 in context. Hubble spectroscopically confirmed the farthest away galaxy to date. {NASA, ESA, P. Oesch and B. Robertson (University of California, Santa Cruz), and A. Feild (STScI)}

In addition representing cutting-edge science — and enabling much more — these looks into the most distant cosmic past offer a taste of what the James Webb Space Telescope, now scheduled to launch in 2021, is designed to explore.  It will have greatly enhanced capabilities to explore in the infrared, which will advance ultra-deep space observing.

But putting aside the cosmic mysteries that ultra deep space and time astronomy can potentially solve, the images available today from Hubble and other telescopes are already more than enough to fire the imagination about what is out there and what might have been out there some millions or billions of years ago.

A consensus of exoplanet scientists holds that each star in the Milky Way galaxy is likely to have at least one planet circling it, and our galaxy alone has billions and billions of stars.  That makes for a lot of planets that just might orbit at the right distance from its host star to support life and potentially have atmospheric, surface and subsurface conditions that would be supportive as well.

A look these deep space images raises the question of how many of them also house stars with orbiting planets, and the answer is probably many of them.  All the exoplanets identified so far are in the Milky Way, except for one set of four so far.

Their discovery was reported earlier this year by Xinyu Dai, an astronomer at the University of Oklahoma, and his co-author, Eduardo Guerras.  They came across what they report are planets while using NASA’s Chandra X-ray Observatory to study the environment around a supermassive black hole in the center of a galaxy located 3.8 billion light-years away from Earth.

In The Astrophysical Journal Letters , the authors report the galaxy is home to a quasar, an extremely bright source of light thought to be created when a very large black hole accelerates material around it. But the researchers said the results of their study indicated the presence of planets in a galaxy that lies between Earth and the quasar.

Furthermore, the scientists said results suggest that in most galaxies there are hundreds of free-floating planets for every star, in addition to those which might orbit a star.

The takeaway for me, as someone who has long reported on astrobiology and exoplanets, is that it is highly improbable that there are no other planets out there where life occurs, or once occurred.

As these images make clear, the number of planets that exist or have existed in the universe is essentially infinite.  That no others harbor life seems near impossible.

 

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Breakthrough Findings on Mars Organics and Mars Methane

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The Curiosity rover on Mars takes a selfie at a site named Mojave. Rock powdered by the rover drill system and then intensively heated rock and then heated to as much as 800 degrees centigrade produced positive findings for long-sought organics. (NASA/JPL-Caltech/MSSS.)

A decades-long quest for incontrovertible and complex Martian organics — the chemical building blocks of life — is over.

After almost six years of searching, drilling and analyzing on Mars, the Curiosity rover team has conclusively detected three types of naturally-occurring organics that had not been identified before on the planet.

The Mars organics Science paper, by NASA’s Jennifer Eigenbrode and much of the rover’s Sample Analysis on Mars (SAM) instrument team, was twinned with another paper describing the discovery of a seasonal pattern to the release of the simple organic gas methane on Mars.

This finding is also a major step forward not only because it provides ground truth for the difficult question of whether significant amounts of methane are in the Martian atmosphere, but equally important it determines that methane concentrations appear to change with the seasons. The implications of that seasonality are intriguing, to say the least.

In an accompanying opinion piece in Science, Inges Loes ten Kate of Utrecht University in  Netherlands wrote of the two papers: “Both these findings are breakthroughs in astrobiology.”

The clear conclusion of these (and other) recent findings is that Mars is not a “dead” planet where little ever changes.  Rather, it’s one with cycles that appear to produce not only methane but also sporadic surface water and changing dune formations.

Remains of 3.5 billion-year old lake that once filled Gale Crater. NASA scientists concluded early in the Curiosity mission that the planet was habitable long ago based on the study of mudstone remains like these. (NASA/JPL-Caltech/MSSS)

Finding organic compounds on Mars has been a prime goal of the Curiosity rover mission.

Those carbon-based compounds surely fall from the sky on Mars, as they do on Earth and everywhere else, but identifying them has proven illusive.

The consequences of that non-discovery have been significant.  Going back to the Viking missions of 1976, scientists concluded that life was not possible on Mars because there were no organics, or none that were detected.

Jen Eigenbrode, research astrobiologist at NASA’s Goddard Space Flight Center. (NASA/W. Hrybyk)

But the reasons for the disappearing organics are pretty well understood.  Without much of an atmosphere to protect it, the Martian surface is bombarded with ultraviolet radiation, which can destroy organic compounds.  Or, in the case of the samples discovered by the SAM team, large organic macromolecules — the likes of proteins, membranes and DNA — are broken up into much smaller pieces.

That’s what the team found, Eigenbrode told me. The organics were probably preserved, she said, because of exceptionally high levels of sulfur present in that part of Gale Crater.

The organics, extracted from mudstone at the Mojave and Confidence Hill sites, had bonded tightly with ancient non-organic material.  The organic material was freed to be collected as gas only after being exposed to temperatures of more than 500 to 800 centigrade in the SAM oven.

“This material was buried for billions of years and then exposed to extreme surface conditions, so there’s a limit to what we can learn about.  Did it come from life?  We don’t know.

“But the fact we found the organic carbon adds to the habitability equation.  It was in a lake environment that we know could have supported life.  Organics are things that organisms can eat.”

It will take different kinds of instruments and samples from drilling deeper into the extreme Martian surface to answer the question of whether the organics came from living microbes.  But for Eigenbrode, future answers of either “yes” or “no” are almost equally interesting.

Finding clear signs of early Martian life would certainly be hugely important, she said.  But a conclusion that Mars never had life — although it had conditions some 3.5 to 3.8 billion years ago quite similar to conditions on Earth at that time — raises the obvious question of “why not?”

NASA’s Curiosity rover raised robotic arm with drill pointed skyward while exploring Vera Rubin Ridge at the base of Mount Sharp inside Gale Crater. This navcam camera mosaic was stitched from raw images taken on Sol 1833, Oct. 2, 2017 and colorized. (NASA/JPL-Caltech/Ken Kremer, Marco Di Lorenzo)

Organic molecules are the building blocks of all known life on Earth, and consist of a wide variety of molecules made primarily of carbon, hydrogen, and oxygen atoms. However, organic molecules can also be made by chemical reactions that don’t involve life.

Examples of non-biological sources include chemical reactions in water at ancient Martian hot springs or delivery of organic material to Mars by interplanetary dust or fragments of asteroids and comets.

It needs to be said that today’s Mars organics announcement was not the first we have heard.  In 2014, a NASA team reported the presence of chlorine-based organics in Sheepbed mudstone at Yellowknife Bay, the first ancient Mars lake visited by Curiosity.

That work, led by NASA Goddard scientists Caroline Freissinet and Daniel Glavin and published in the Journal of Geophysical Research, focused on signatures from unusual organics not seen naturally on Earth.

The organics were complex and made entirely of Martian components, the paper reported.  But because they combined chlorine with the organic hydrocarbons, they are not considered to be as “natural” as the discovery announced today.

And when it comes to organics on Mars, the complicated history of research into the presence of the gas methane (a simple molecule that consists of carbon and hydrogen) also shows the great challenges involved in making these measurements on Mars.

By measuring absorption of light at specific wavelengths, the tunable laser spectrometer on Curiosity measures concentrations of methane, carbon dioxide and water vapor in the Martian atmosphere. (NASA)

 

The gold-plated Sample Analysis on Mars contains three instruments that make the measurements of organics and methane.  (NASA/Goddard Space Flight Center)

The second Science paper, authored by Chris Webster of NASA’s Jet Propulsion Lab and colleagues, reports that the gas methane has been detected regularly in recent years, with surprising seasonality.

“The history of Mars methane has been frustrating, with reports of some large plumes and spikes detected, but none have been repeatable.  It’s almost like they’re random,” he told me.  “But now we can see a large seasonal cycle in the background of these detections, and that’s extremely important.”

Over three Mars years, or almost five Earth years, Webster said there have been significant increases in methane detected during the summer, and especially the late summer. That tripling of the methane counts is considered too great to be random, especially since the count declines as predicted after the summer ends.

No definite explanation of why this happens has emerged yet, but one theory has been embraced by some scientists.

While it is still cold in the Martian summer, it can get warm enough where the sun shines directly on a collection of ice for some melting to occur.  And that melting, the paper reports, could provide an escape valve for methane collected long ago under the surface.  The process is termed “microseepage.”

 

This illustration shows the ways in which methane from the subsurface might find its way to the
surface where its release could produce the large seasonal variation in the atmosphere
as observed by Curiosity. Potential methane sources include byproducts from organisms alive or long dead, ultraviolet degradation of organics, or water-rock chemistry; and its losses include atmospheric photochemistry and surface reactions. Seasons refer to the northern hemisphere. The plotted data is from Curiosity’s TLS-SAM instrument, and the curved line through the data is to aid the eye. (NASA/JPL-Caltech)

Methane is a crucial organic in astrobiology because most of that gas found on Earth comes from biology, although various non-biological processes can produce methane as well.

Today’s paper by Webster et al is the third in Science on Mars methane as measured by Curiosity, and it is the first to find a seasonal pattern.  The first paper, in 2013,  actually reported there was no methane measured in early runs, a conclusion that led to push-back from many of those working in the field.

While the Mars methane results released today are being described as a “breakthrough,” they follow closely the findings of a Science paper in 2009 by Michael Mumma and Geronimo Villanueva, both at NASA Goddard.

The two reported then similar findings of plumes of methane on Mars, of a seasonality associated with their distribution, and a similar conclusion that the methane probably was coming from subsurface reservoirs.  Like Webster et al, Mumma and Villanueva said they were unable to determine if the source of methane was biological or geological.

The methane levels in the plumes they found were considerably higher than detected so far by Curiosity, but what they were detecting was quite different.  Using ground-based telescopes, they detected the high concentrations in two specific areas over a number of years, while Curiosity is measuring methane levels that are more global or regional.

Red areas indicate where in 2003 ground-based observers detected concentrations of methane in the Martian atmosphere, measured in parts per billion (ppb).  (NASA / M. Mumma & others)

Just as Webster was criticized for his initial paper saying there was no methane detected on Mars, the Mumma team also got sharp questions about their methodology and conclusions.  This grew as their numerous follow-up efforts to detect the Mars methane proved unsuccessful.

But now Webster says the Curiosity findings have essentially “confirmed” what Mumma and Villanueva reported nine years ago.

Still, the Curiosity results are a breakthrough because they were made on Mars rather than through a telescope. Mumma, who described the new Curiosity results as “satisfying,” agreed that they were a major step forward.

“This is how science works,” he said.  “We do our work and put out our papers and other scientists react.  We take it all in and make changes if needed.  But the big changes come when new, and maybe different, data is presented.”

And that’s exactly what will be happening soon regarding methane on Mars.  Beginning early this year, the European/Russian Trace Gas Orbiter (TGO) has been collecting data specifically on Mars gases including methane.  Unlike previous Mars methane campaigns, this one can potentially determine whether the methane being released from below the surface was formed by biology or geology — although not without great difficulty.

Mumma, who is part of that TGO team, said the first release of information is due in the fall.

 

 

 

 

 

 

 

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Exoplanet Fomalhaut b On the Move

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Enlarge and enjoy.  Fomalhaut b on its very long (1,700 year) and elliptica orbit, as seen here in five images taken by the Hubble Space Telescope over seven years.  The reference to “20 au” means that the bar shows a distance of 20 astronomical units, or 20 times the distance from the sun to the Earth. (Jason Wang/Paul Kalas; UC Berkeley)

Direct imaging of exoplanets remains in its infancy, but goodness what a treat it is already and what a promise of things to come.

Almost all of the 3,714 exoplanets confirmed so far were detected via the powerful but indirect transit and radial velocity methods — measures of slightly decreased light as a planet crosses in front of its star, or the measured wobble of a star caused by the gravitational pull of a planet.

But now 44 planets have also been detected by telescopes — in space and on the ground — looking directly at distant stars.  Using increasingly sophisticated coronagraphs to block out the blinding light of the stars, these tiny and often difficult-to-identify specks are nonetheless results that are precious to scientists and the public.

To me, they make exoplanet science accessible as perhaps nothing else so far.  Additionally, they strike me as moving — and I don’t mean in orbit.  Rather, as when you see your own insides via x-rays or MRIs, direct imaging of exoplanets provides a glimpse into the otherwise hidden realities of our world.

And in the years ahead – actually, most likely the decades ahead — this kind of direct imaging of our astronomical neighborhood will become increasingly powerful and common.

This is how the astronomers studying the Fomalhaut system describe what you are seeing:

“The Fomalhaut system harbors a large ring of rocky debris that is analogous to our Kuiper belt. Inside this ring, the planet Fomalhaut b is on a trajectory that will send it far beyond the ring in a highly elliptical orbit.

“The nature of the planet remains mysterious, with the leading theory being the planet is surrounded by its own ring or a sphere of dust.”

 

A simulation of one possible orbit for Fomalhaut b derived from the analysis of Hubble Space Telescope data between 2004 and 2012, presented in January 2013 by astronomers Paul Kalas and James Graham of Berkeley, Michael Fitzgerald of UCLA and Mark Clampin of NASA/Goddard. (Paul Kalas)

Fomalhaut b was first described in 2008 by Paul Kalas, James Graham and colleagues at the University of California, Berkeley.   If not the first object identified through direct imaging — a brown dwarf failed star preceded it, as well as other objects that remain planet candidates — Fomalhaut was among the very first.  The data came via the Advanced Camera for Surveys on the Hubble Space Telescope.

But Fomalhaut b is an unusual planet by any standard, and that resulted in a lot of early debate about whether it really was a planet.  Early efforts to confirm the presence of the planet failed, in part because the efforts were made in the infrared portion of the spectrum.

Instead, Fomalhaut b had been detected only in the optical portion of the spectrum, which is uncommon for a directly imaged planet. More specifically, it reflects bluish light, which again is unusual for a planet.  Some contended that the planet detection made by Hubble was actually a noise artifact.

A pretty serious debate ensued in 2011 but by 2013 the original Hubble data had been confirmed by two teams and its identity as a planet was broadly embraced, although the noise of the earlier debate to some extent remains.

As Kalas told me, this is probably because “no one likes to cover the end of a debate.”  Nonetheless, he said, it is over.

“Fomalhaut b at age 440 Myr (.44 billion years) is much older than the other directly imaged planets,” Kalas explained. “The younger the planet, the greater the infrared light it emits. Thus it is not particularly unusual that it is hard to image planets in the Fomalhaut system using infrared techniques.”

Kalas believes that a ring system around the planet could be reflecting the light.  Another possibility, he said, is that two dwarf planets collided and a compact dust cloud surrounding a dwarf planet is moving through the Fomalhaut system.

That scenario would be very difficult to test, he said, but the alternate possibility of a Saturnian exoplanet with a ring is something that the James Webb Space Telescope will be able to explore.

In any case, the issue of whether or not the possibly first directly-imaged planet is in fact a planet has been resolved for now.

When the International Astronomical Union held a global contest to name some of the better known exoplanets several years ago, one selected for naming was Fomalhaut b, which also now has the name “Dagon.”  The star Fomalhaut is the brightest in the constellation Pisces Australis — the Southern Fish — and Dagon was a fish god of the ancient Philistines.

 

This video of Beta Pictoris and its exoplanet was made using nine images taken with the Gemini Planet Imager over more than two years years.  The planet is expected to come our from behind its star later this year, and the GPI team hopes to capture that event. (Jason Wang; UC Berkeley, Gemini Planet Imager Exoplanet Survey)

While instruments on the W.M. Keck Observatory in Hawaii, the European Very Large Telescope in Chile and the Hubble Space Telescope have succeeded in directly imaging some planets, the attention has been most focused on the two relatively newcomers.  They are the Gemini Planet Imager (GPI), now on the Gemini South Telescope in Chile and funded largely by American organizations and universities, and the largely European Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument, also in Chile.

In real time, the two instruments correct for distorting atmospheric turbulences around Earth and also block the intense light of the host stars. Any residual incoming light is then scrutinized, and the brightest spots suggest a possible planet and can be photographed as such.

The ultimate goal is have similar instruments improved until they are powerful enough to read the atmospheres of the planets through spectroscopy, which has been done so far only to a limited extent.

Kalas, Graham and Jason Wang (a graduate student at Berkeley who put together the direct imaging movies ) are part of the GPI team, which since 2014 has been searching for Jupiter-sized and above planets orbiting some distance from their suns.  The group is a member of NASA’s NExSS initiative to encourage exoplanet scientists from many disciplines to work together.

While GPI has had successes detecting important exoplanets such as 51 Eridani b, it also studies already identified planets to increase understanding of their orbits and their characteristics.

The Gemini Planet Imager when it was being connected to the Gemini South Telescope in Chile. (Gemini Observatory)

GPI has been especially active in studying the planet Beta Pictoris b, a super Jupiter discovered using data collected by the European Southern Observatory Very Large Telescope.  While the data was first collected in 2003, it took five years to tease out the planet orbiting the young star and it took several more years to confirm the discovery and begin characterizing the planet.

GPI has followed Beta Pictoris b for several years now, compiling orbital and other data used for video above.

The planet is currently behind its sun and so cannot be observed.  But James Graham told me that the planet is expected to emerge late this year or early next year.  It remains unclear, Graham said, whether GPI will be able to capture that emergence because it will soon be moved from the Gemini telescope in Chile to the Gemini North Telescope on Hawaii.  But he certainly hopes that it will be allowed to operate until the planet reappears.

The planet 51 Eridani b was the first exoplanet discovered by the GPI and remains one of its most important.   The planet is a million times fainter than its parent star and shows the strongest methane signature ever detected on an alien planet, which should yield additional clues as to how the planet formed.

The four-year GPI campaign from Chile has not discovered as many Jupiter-and-greater sized planets as earlier expected.  Graham said that may well be because there are fewer of them than astronomers predicted, or it may be because direct imaging is difficult to do.

But Graham said the campaign is actually nowhere near over.  Much of the data collected since 2014 remains to be studied and teased apart, and other Jupiters and super Jupiters likely are hidden in the data.

Right now the exoplanet science community, and especially those active in direct imaging, are anxiously awaiting a decision by NASA, and then Congress, about the fate of the Wide Field Infrared Survey Telescope (WFIRST.)

Designed to be the first space telescope to carry a coronagraph and consequently a major step forward for direct imaging, it was scheduled to be NASA’s big new observatory of the 2020s.

But the Trump Administration cancelled the mission earlier this year, Congress then restored it but with the caveat that NASA had to provide a detailed plan for its science, its technology and its cost.  That plan remains an eagerly-awaited work in progress.

Meanwhile, here is another example of what direct imaging, with the help of soon-to-be Caltech postdoc Jason Wang, can provide.  The video of the HR 8799 system went viral when first made public in early last year.

 

The four planet system orbiting the planet HR 8977, first partially identified in 2008 by Christian Marois of the National Research Council of Canada’s Herzberg Institute of Astrophysics and Bruce Macintosh of Stanford and others.   The video was created in 2017 after all four planets had been identified via direct imagine and their orbits had been followed for some years. (Jason Wang of UC Berkeley/Christian Marois of NRC Herzberg.)

The promise of direct imaging is enormous.  The collected photons can be used for spectroscopy that can potentially tell scientists about a planet’s radius, mass, age, effective temperature, clouds, molecular composition, rotation rate and atmospheric dynamics.

For a small, potentially habitable planet, direct imaging can measure surface temperate and pressure and determine whether it can support liquid water.  It can also potentially determine if the atmosphere is in the kind of disequilibrium regarding oxygen, ozone and perhaps methane that signal the presence of life.

But almost all this is in the future since none of the current instruments are powerful enough to collect that data.

In the meantime, researchers such as Berkeley graduate student Lea Hirsch, soon to be a Stanford postdoc,  are focused on using the strengths of the different detection methods to come up with constraints on exoplanetary characteristics (such as mass and radius) that one technique alone could not provide.

University of California at Berkeley astronomy grad student Lea Hirsch at Lick Observatory. She will be going soon to Stanford University for a postdoc with Gemini Planet Imager Principal Investigator Bruce Macintosh.

For instance, the transit technique works best for identifying planets close to their stars, direct imaging is the opposite and radial velocity is best that detecting large and relatively close-in planets.  Radial velocity gives a minimum (but not maximum) mass, while transits provide an exoplanet radius.

What Hirsch would like to do is determine constraints (limits) on the size of exoplanets using both radial velocity measurements and direct imaging.

As she explained, radial velocity will give that minimum mass, but nothing more in terms of size.  But in an indirect way for now, direct imaging can provide some maximum mass.

If, for instance, astronomers know through the radial velocity method that exoplanet X orbits a certain star and is twice the size of Jupiter, they can then look for it using direct imaging with confidence that something is there.  Let’s say the precision of the imaging is such that if a planet six times the size of Jupiter was present they would — over a period of time — detect it.

A detection would indeed be great and the planet’s mass (and more) would then be known.  But if no planet is detected — as often happens — then astronomers still collect important information.  They know that the planet they are looking for is less than six Jupiter masses.  Since the radial velocity method already determined it was at least larger than two Jupiters, scientists would then know that the planet has a mass of between two and six Jupiters.

“All the techniques in our toolkit {of exoplanet searching} have their strengths and weaknesses,” she said.  “But using those techniques together is part of our future because there’s a potential to know much more.”

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Diamonds and Science: The Deep Earth, Deep Time, and Extraterrestrial Crystal Rain

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Deep Earth diamond with garnet inside.  These inclusions, which occur during the diamond formation process, provide not only a way to date the diamonds, but also a window into conditions in deep Earth when they wee formed.  (M. Gress, VU Amsterdam)

We all know that cut diamonds sparkle and shine, one of the great aesthetic creations from nature.

Less well known is that diamonds and the bits of minerals, gases and water encased in them offer a unique opportunity to probe the deepest regions of our planet.

Thought to be some of the oldest available materials found on Earth — some dated at up to 3.5 billion years old — they crystallize at great depth and under great pressure.

But from the point of view of those who study them, it’s the inclusions that loom large because allow them to know the age and depth of the diamond’s formation. And some think they can ultimately provide important clues to major scientific questions about the origin of water on Earth and even the origin of life.

The strange and remarkable subterranean world where the diamonds are formed has, of course, never been visited, but has been intensively studied using a variety of indirect measurements.  And this field has in recent weeks gotten some important discoveries based on those diamond inclusions.

First is the identification by Fabrizio Nestola of the Department of Geosciences at the University of Padua and colleagues of a mineral that has been theorized to be the fourth most  common on Earth, yet had never been found in nature or successfully synthesized in a laboratory.  As reported in the journal Nature, the mineral is a variant of calcium silicate (CaSiO3), created at a high pressure that gives it a uniquely deep-earth crystal structure called “perovskite,” which is the name of a mineral, too.

Mineral science does not allow a specimen to be named until it has actually been found in name, and now this very common form of mineral finally will get a name. But more important, it moves forward our understanding of what happens far below the Earth’s surface.

 

 

Where diamonds are formed and found on Earth. The super-deep are produced very far into the mantle and are pushed up by volcanoes and convection  The lithospheric diamonds are from the rigid upper mantle and crust and the alluvial diamonds are those which came to the surface and then were transported elsewhere by natural forces. (Fabrio Nestola, Joseph R Smyth)

 

The additional discovery was of a tiny bit of water ice known as ICE-VII inside several other deep diamonds.  While samples of H2O ice have been identified in diamonds before, none were ICE-VII which is formed only under tremendous deep-Earth pressure.

In addition to being a first, the ICE-VII discovery adds to the growing confidence of scientists that much H2O remains deep underground, with some inferring as much deep subsurface water as found in the surface oceans.  That paper was authored by University of Nevada, Las Vegas geoscientist Oliver Tschauner and colleagues, and appeared in the journal Science.

Diamonds are a solid form of carbon with a distinctive cubic crystal structure.  They are generally formed at depths of 100 to 150 miles in the Earth’s mantle, although a few have come from as deep as 500 to 600 miles down.  (And some come from space, as described in this article below and in a just published Nature Communications article about diamonds in the Almahata Sitta meteorite that crashed in Sudan in 2006.)

Those super-deep Earth diamonds form in a cauldron up to 1,000 degrees F and at 240,000 times the atmospheric pressure at sea level.  They are made from carbon-containing fluids that dissolve minerals and replace them with what over time become diamonds.

Much more recently (tens to hundreds of million years ago), the would have been pushed to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites (blue-tinged in color and coarse grained) and lamproites (rich in potassium and also from deep in the mantle.)

The mantle – which makes up more than 80 percent of the Earth’s volume – is made of silicate minerals containing iron, aluminum, and calcium among others.  Blue diamonds are that color because of the presence of the trace mineral boron in the mantle.

And now we can add water the list as well.

 

Professor of Mineralogy Fabrizio Nestola presented on his recent work in advances in X-ray crystallography on diamonds and their inclusions in a talk title “Diamond, A Journey to the Center of the Earth.” One of his collaborators on the recent high-pressure calcium silicate paper is mantle geochemist Graham Pearson of the University of Alberta, where Nestola was recently a visiting professor. (RadioBue.it)

Nestola, who has been conducting his deep-Earth studies with a major grant from the European Union, is eager to take his already substantial work much further.

First he is looking for answers to the basic question of the origin of water on Earth (from incoming asteroids and comets or an integral component at formation) and ultimately to the origin of life.  Diamonds, he says, offer a pathway to study both subjects.

For water, his goal is to find a range of diamond-encircled samples that can be measured for their deuterium to hydrogen ratio — a key diagnostic to determining where in the solar system an object and its H2O originated,  Deuterium, or heavy hydrogen, is an isotope of hydrogen with an extra neutron.

An example of a super-deep diamond from the Cullinan Mine, where scientists recently discovered a diamond that provides first evidence in nature of Earth’s fourth most abundant mineral–calcium silicate perovskite. (Petra Diamonds)

As the number of diamond samples with evidence of water grows, Nestola says it will be possible to determine how the D/H ratio changes over time and as a result gain a better understanding of where the Earth’s water came from.

When it comes to clues regarding the origin of life, Nestola will be looking for carbon isotopes in the diamonds.

“Actually, it cannot be excluded that carbon from a primordial organic matter can even travel to the lower mantle,” he told me. “The oldest diamonds were dated 3.5-3.6 billion years, so it would be fantastic to detect a carbon isotope signature of surface carbon in a 3.5 billion years diamond.  This could provide very strong input for the origin of life.”

Regarding the high-pressure form of calcium silicate that he and his colleagues recently identified, Nestola said that many scientists have tried to reproduce it in their labs but have found there’s no way to keep the mineral stable at surface pressures.  So the discovery had to be made from inside the nearly impermeable container of a diamond.

The diamond that contained the common yet never before found mineral was just 0.031 millimeters across, is also a super-rare specimen.

Adding to the interest in this discovery is that other trace minerals and elements found in the inclusion strongly suggest that the material was once on the Earth’s crust.  The logic is that it would have been subducted as a function of plate tectonics billions of years ago, then encased in a forming diamond deep in the mantle, and ultimately sent back up near the surface again.

Most diamonds are born much closer to Earth’s surface, between 93 and 124 miles deep. But this particular diamond would have formed at a depth of around 500 miles, the researchers said.

“The diamond keeps the mineral at the pressure where it was formed, and so it tells us a lot about the ancient deep-Earth environment,” Nestola said.  “This is how we’ll learn about deep Earth and ancient Earth.  And we hope about those central origin questions too.”

 

A South African diamond crystal on kimberlite, an igneous rock formed deep in the mantle and famous for the frequency with which it contains diamonds. (Shutterstock)

For his ICE-VII study, Tschauner used diamonds found in China, the Republic of South Africa, and Botswana that had been pushed up from inside Earth.  He believes the range of locations strongly suggests that the presence of the ICE-VII is a global phenomenon.

Scientists theorize the diamonds used in the study were born in the mantle under temperatures reaching more than 1,000-degrees Fahrenheit.

“One essential question that we are working on is how much water is actually stored in the mantle.  Is it oceans, or just a bit?” Tschauner said. “This work shows there can be free excess fluids in the mantle, which is important.”

The mantle is a vast reservoir of mostly solid and very hot rock under immense pressure beneath the crust. It has an upper layer, a transition zone, and a lower layer. The upper layer has a little bit of water, but scientist estimate 10 times more water may be in the transition zone, where the enormous pressure is changing crystal structures and minerals seem to be more soluble. Minerals in the lower layer don’t seem to hold water as well.

There’s already evidence of water in the mantle in different forms, such as water that has been broken up and incorporated into other minerals. But these diamonds contain water frozen into a special kind of ice crystal. There are lots of different ways water can crystallize into ice, but ice-VII is formed under higher pressures.

While the diamond was forming, it must have encapsulated some liquid water from around the transition zone. The high temperatures prevented this water from crystalizing under the high pressures. As geologic activity moved the diamonds to the surface, they maintained the high pressures in their rigid crystal structures—but the temperature dropped. This would have caused the water to freeze into ice-VII.

The discovery of Ice-VII in the diamonds is the first known natural occurrence of the aqueous fluid from the deep mantle. Ice-VII had been found as a solid in prior lab testing of materials under intense pressure. As described before,  it begins as a liquid in the mantle.

“These discoveries are important in understanding that water-rich regions in the Earth’s interior can play a role in the global water budget and the movement of heat-generating radioactive elements,” Tschauner said.

This discovery can help scientists create new, more accurate models of what’s going on inside the Earth, specifically how and where heat is generated under the Earth’s crust.

 “It’s another piece of the puzzle in understanding how our planet works,” Tschauner said.

A polished and enlarged section of the Esquel pallasite meteoritemeteorite that delivered tiny nano-diamonds to Earth. This is a common occurrence, as there is believed to be substantial amounts of high-pressure carbon in the galaxies, and thus some diamonds. (Trustees of the NHM, London)

The diamonds studied by researchers such as Nestola and Tschauner not the sort that would ever go to the market.  “They are very bad diamonds, bad for jewelers,” Nestola said, “but precious for geologists.”

Diamonds are by no means exclusive to Earth, and are becoming a significant area of study for planetary exoplanet scientists, too.

Not only are they contained in minute form in meteorites, but atmospheric data for the gas giant planets indicates that carbon is abundant in its famous hard crystal form elsewhere in the solar system and no doubt beyond.

Lightning storms turn methane into sooty carbon which, as it falls, hardens under great pressure into graphite and then diamond.

These diamond “hail stones” eventually melt into a liquid sea in the planets’ hot cores, researchers told a an American Astronomical Society conference in 2013.

The biggest diamonds would likely be about a centimeter in diameter – “big enough to put on a ring, although of course they would be uncut,” says Dr Kevin Baines, of the University of Wisconsin-Madison and NASA’s Jet Propulsion Laboratory.

“The bottom line is that 1,000 tons of diamonds a year are being created on Saturn. People ask me – how can you really tell? Because there’s no way you can go and observe it.

“It all boils down to the chemistry. And we think we’re pretty certain.”

These potential raining diamonds, and all sorts of other extraterrestrial diamonds including possible diamond worlds, doubtless have their own scientifically compelling and important stories to tell.

 

 

 

 

 

 

 

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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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