Category: The Search for Life Beyond Earth (page 1 of 6)

Viruses, the Virosphere and Astrovirology

An electron microscopic image of the 2019 novel coronavirus grown in cells at The University of Hong Kong.  Thin-section electron micrographs of the novel coronavirus show part of an infected cell, grown in a culture, with virus particles being released from the cell’s surface. (The University of Hong Kong)

 

When the word “virus” first came into use, it was as a “poison” and “a very small disease-causing agent.”  While the presence of viruses was theorized earlier, they were not fully identified until the 1890s.

So from their earliest discovery, viruses were synonymous with disease and generally of the ghastly epidemic type of disease we now see with coronavirus.  Few words carry such a negative punch.

Without in any way  minimizing the toll of viruses on humans (and apparently all other living things,) men and women who study viruses know that this association with disease is far too restrictive and misses much of what viruses do.  It’s perhaps not something to argue while a viral pandemic is raging, but that’s when the focus on viruses is most intense.

Here, then, is a broader look at what viruses do and have done — how they inflict pandemics but also have introduced genes that have led to crucial evolutionary advances, that have increased the once-essential ability of cyanobacteria in early Earth oceans to photosynthesize and produce oxygen, and that have greatly enhanced the immunity systems of everything they touch.  They — and the virosphere they inhabit — have been an essential agent of change.

Viruses are also thought to be old enough to have played a role — maybe a crucial role — in the origin of life, when RNA-like replicators outside cells may have been common and not just the domain of viruses.  This is why there is a school of thought that the study of viruses is an essential part of astrobiology and the search for the origins of life.  The field is called astrovirology.

Viruses are ubiquitous — infecting every living thing on Earth.

Virologists like to give this eye-popping sense of scale:  based on measurements of viruses in a liter of sea water, they calculate the number of viruses in the oceans of Earth to be 10 31.  That is 10 with 31 zeros after it.  If those viruses could be lined up, the scientists have calculated, they would stretch across the Milky Way 100 times.

“The vast majority of viruses don’t care about humans and have nothing to do with them,” said Rika Anderson,  who studies viruses around hydrothermal vents and teaches at Carleton College in Minnesota. … Read more

Theorized Northern Ocean of Mars; now long gone.  (NASA)

Change is the one constant in our world– moving in ways tiny and enormous,  constructive and destructive.

We’re living now in a time when a rampaging pandemic circles the globe and when the climate is changing in so many worrisome and potentially devastating ways.

With these ominous  changes as a backdrop, it is perhaps useful to spend a moment with change as it happens in a natural world without humans.  And just how complete that change can be:

For years now, planetary scientists have debated whether Mars once had a large ocean across its northern hemisphere.

There certainly isn’t one now — the north of Mars is parched, frigid and largely featureless.  The hemisphere was largely covered over in a later epoch by a deep bed of lava, hiding signs of its past.

The northern lowlands of Mars, as photographed by the Viking 2 lander. The spacecraft landed in the Utopia Planitia section of northern Mars in 1976. (NASA/JPL)

Because our sun sent out significantly less warmth at the time of early Mars (4.2-3.5  billion years ago,) climate modelers have long struggled to come up with an explanation for how the planet — on average, 137 million miles further out than Earth — could have been anything but profoundly colder than today. And if that world was so unrelentingly frigid, how could there be a surface ocean of liquid water?

But discoveries in the 21st century have strongly supported the long-ago presence of water on a Mars in the form of river valleys, lakes and a water cycle to feed them.  The work done by the Curiosity rover and Mars-orbiting satellites has made this abundantly clear.

An ocean in the northern lowlands is one proposal made to explain how the water cycle was fed.

And now, In a new paper in Journal of Geophysical Research: Planets,  scientists from Japan and the United States have presented modelling and analysis describing how and why Mars had to have a large ocean early in its history to produce the geological landscape that is being found.

Lead author Ramses Ramirez, a planetary scientist with the Earth-Life Science Institute in Tokyo, said it was not possible to determine how long the ocean persisted, but their team concluded that it had to be present  in that early period around 4 billion to 3.5 billion years ago.  That is roughly when what are now known to be river valleys were cut in the planet’s southern highlands.… Read more

Planetary Protection and the Moons of Mars

Mars with its two moons, Phobos and Deimos. Phobos orbits a mere 3,700 mile3s (6,000 km) above the surface, while Deimos is almost 15,000 miles (24,000 kilometers) away from the planet. In comparison, there is an almost 384,000 kilometers mean distance between the surface of the Earth and our elliptically orbiting moon. With the moons so close to Mars, debris from meteorite impacts on the planet can easily land on the moons. (NASA/JPL-Caltech/University of Arizona)

Sometime in the early to mid-2020s, the capsule of the Japanese Martian Moons eXploration (MMX) mission is scheduled to arrive at the moons of Mars – Phobos and Deimos.

These are small and desolate places, but one goal of the mission is large: to collect samples from the moons and bring them back to Earth.

If it succeeds, the return would likely be the first ever from Mars or its moons — since planned sample return efforts from the planet itself will be considerably more challenging and so will take longer to plan and carry out.

The Mars moon mission has the potential to bring back significant information about their host planet, the early days of our solar system, and the origins and make-up of the moons themselves.

It also has the potential, theoretically at least, to bring back Martian life, or signatures of past Martian microbial life. And similarly, it has the potential to bring Earth life to one of the moons.

Hidenori Genda, an ELSI planetary scientist with a long-lasting interest in the effects of giant planetary impacts, such as the one that formed our moon. His work has also focused on atmospheres, oceans, and life beyond Earth. (Nerissa Escanlar)

Under the general protocols of what is called “planetary protection,” this is a paramount issue and is why the Japan Aerospace Exploration Agency (JAXA) was obliged to assess the likelihood of any such biological transfers with MMX.

To make that assessment, the agency turned to a panel of experts that included planetary scientist, principal investigator, and associate professor Hidenori Genda of Tokyo’s Earth-Life Science Institute.

The panel’s report to JAXA and the journal Life Sciences in Space Research concluded that microbial biology (if it ever existed) on early Mars could have been kicked up by incoming meteorites, and subsequently traveled the relatively short distance through space to land on Phobos and Deimos.

However, the panel’s conclusions were unambiguous: the severe radiation these microbes would encounter on the way would make sure anything once living was now dead.… Read more

Exploring Our Sun Will Help Us Understand Habitability

The surface of the sun, with each “kernel” or “cell” roughly the size of Texas. The movie is made up of images produced by the Daniel Inouye SolarTelescope in Hawaii.  Novel and even revolutionary data and images are also expected from the Parker Solar Probe (which will travel into the sun’s atmosphere, or corona) and the just launched Solar Orbiter, which will study (among many other things) the sun’s polar regions. (NSO/NSF/AURA)

 

Scientists have been  studying our sun for centuries, and at this point know an awful lot about it — the millions of degrees Fahrenheit heat that it radiates out from the corona, the tangled and essential magnetic fields that it creates, the million-miles-per-hour solar wind and the charged high-energy solar particles that can be so damaging to anything alive.

But we have now entered a time when solar science is taking a major leap forward with the deployment of three pioneering instruments that will explore the sun and its surroundings as never before.  One is a space telescopes that will get closer to the sun (by far) than any probe before, another is a probe that will make the first observations of the sun’s poles, and the third is a ground-based solar telescope that can resolve the sun in radically new ways — as seen in the image above, released last month.

Together, NASA’s Parker Solar Probe, the joint European Space Agency-NASA Solar Orbiter mission and the National Science Foundation’s Inouye Solar Telescope on Hawai’i will provide pathways to understand some of the mysteries of the sun.  They include resolving practical issues involving the dynamics  of “space weather” that can harm astronauts and telecommunications systems, and larger theoretical unknowns related to all the material that stars scatter into space and onto planets.

Some of those unresolved questions include determining how and why heat and energy flow from the sun’s inner core to the outer corona and make it so much hotter, determining the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind, the make-up and effects of solar flares and coronal mass ejections, and how and why the sun is able to create and control the heliosphere — the vast bubble of charged particles blown by the solar wind into interstellar space.

 

An illustration of Kepler2-33b, , one of the youngest exoplanets detected to date using NASA Kepler Space Telescope.

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Big News for SETI Enthusiasts

The CHIME telescope has detected a mysterious repeating radio signal far away in the cosmos – only the second ever identified of its kind.  CHIME is the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is an interferometric radio telescope at the Dominion Radio Astrophysical Observatory in British Columbia, (Danielle Futselaar)

It has been almost 60 years now that scientists — a first a few intrepid souls and now many more — have been searching the skies for radio signals that just might be coming from other advanced, technological civilizations.  There have been some intriguing anomalies that created great interest, but nothing has to date survived further study.

But two recent developments in the this Search for Extraterrestrial Intelligence (SETI) make clear that the lack of alien signals so far has not diminished interest in the field and in the science and technology behind it.  Rather, SETI is alive and doing quite well.

A first sign is scientific and involves what are called “fast radio blasts” or FRBs — high energy pulses that are extremely short lived and, until recently, determined to be sporadic and random.  But a paper last week from a Canadian team reported a series fast radio blast from a galaxy a 500 million light-years away that appeared to be repeating about every 16 days.

The authors put forward a number of astrophysical explanations for this most unusual pattern and shied away from any kind of SETI hypothesis.  More on this later.

But the detection is the kind of radio signal anomaly that SETI scientists and enthusiasts are looking for.  And now they will also have the opportunity to search a vast new trove of data provided by Breakthrough Listen, part of the privately-funded Breakthrough Initiatives.

A sequence of 14 of the 15 fast radio bursts from FRB 121102, the first repeating fast radio burst to be identified, in 2018. The streaks across the colored energy plot are the bursts appearing at different times and different energies because of dispersion caused by 3 billion years of travel through intergalactic space. The bursts were captured in a broad bandwidth via the Breakthrough Listen backend instrument at the Green Bank Telescope. It does not repeat in patterns like the one just discovered by the Canadian team. (Berkeley News.)

At the close of a meeting of the American Association for the Advance of Science (AAAS) on Friday, the Breakthrough team announced the release nearly 2 petabytes (2 million gigabytes) of data, the second massive data dump from the four-year old Breakthrough Listen search for extraterrestrial intelligence

The data, most of it fresh from the telescope prior to detailed study by astronomers, comes from a survey of the radio spectrum between 1 and 12 gigahertz (GHz).… Read more

Using Climate Science on Earth to Understand Planets Beyond Earth

Climate expert Tony Del Genio has just retired after 41 years-plus at NASA’s Goddard Institute of Space Studies (GISS) in New York City. Here Del Genio is attending a Cubs game at Wrigley Field with (from the lower right) Dawn Gelino, Shawn Domogal-Goldman, Aaron Gronstal and Mary Voytek. All are part of the NASA NExSS initiative. (Dawn Gelino)

Anthony Del Genio started out his career expecting to become first an engineer and then a geophysicist.  He was in graduate school at UCLA and had been prepared by previous mentors to enter the geophysics field.  But a 1973 department-wide test focused on seismology, rather than fields that he understood better, and his days as a geophysicist were suddenly over.  Fortunately,  one of his professors saw that he had done very well in the planetary atmospheres and geophysical fluid dynamics sections of the exams, and suggested a change in focus.

That turned out to be a good thing for Del Genio, for the field of climate modeling, and for NASA. Because for the next four decades-plus, Del Genio has been an important figure in the field of climate science — first modeling cloud behavior and climate dynamics on Earth with ever more sophisticated atmospheric general circulation models (GCMs), and then beginning to do the same on planets beyond Earth.

His entry into the world of Venus, Saturn, Titan and distant exoplanets beyond is how I met Tony in 2015. At the same time that Many Worlds began as a column, Del Genio was named one of the founding leaders of the Nexus for Exoplanet System Science (NExSS) — the pioneering, interdisciplinary NASA initiative to bring together scientists working in the field of planetary habitability.  (NExSS also supports this column.)

Del Genio is a hard-driving scientist, but also has a self-deprecating and big-picture, poetic side.  This came across at our first diner breakfast together on Manhattan’s Upper West Side (where GISS is located), and was highlighted in a piece that Del Genio just wrote for a new series initiated by the American Geophysical Union (AGU),  Perspectives of Earth and Space Scientists.   In that series, scientists are asked to look back on their careers and write about their science and journeys.  Del Genio’s perspective is the first in this series, and I will reprint most of its bottom half because I found it so informative and interesting.

But first, a quote from Del Genio’s piece that sets the stage:  “The beauty of science, if we are patient, is that nature reveals its secrets little by little, slowly enough to keep us pressing forward for more but fast enough for us not to despair.”… Read more

How Long Were the Wet Periods on Early Mars, and Was That Water Chemically Suitable For Life?

 

An artist rendering, based on scientific findings, of Gale Crater in Mars during one of its ancient, wet periods. (NASA)

There is no doubt that early Mars had long period of warmer and much wetter climates before its atmosphere thinned too much to retain that liquid H20 on the surface.

As we know from the Curiosity mission to Gale Crater and other orbital findings, regions of that warmer and wetter Mars had flowing water and lakes periodically over hundreds of millions of years.  That’s one of the great findings of planetary science of our times.

But before approaching the question of whether that water could have supported life, a lot more needs to be known than that water was present.  We need answers to questions like how acidic or basic that water likely was?  Was it very salty? Did it have mineral and elemental contents that could provide energy to support any potential life?

And most especially, how long did those wet periods last, and the dry periods as well?

In a recent paper for Nature Communications, some more precise answers are put forward based on data collected at Gale Crater and interpreted based on geochemical modeling and Earth-based environmental science.

The water, say geochemist Yasuhito Sekine of the Earth-Life Science Institute (ELSI) in Tokyo and colleagues from the U.S. and Japan, had many important characteristics supportive of life.  It was only mildly salty, it had a near-neutral pH, it contained essential minerals and elements in state of disequilibrium — meaning that they could give and receive the electrons needed to provide life-supporting energy.   The  area was hardly lush — more like the semi-arid regions of Central Asia and Utah’s Great Salt Lake — but it contained water that was plausibly life supporting.

Based on an analysis of the patterns and quantities of salt remains, they estimate the water was present numerous times for between 10,000 to one million years each period.

Were those warm eras long enough for life to emerge, and the dry period short enough for it to survive?

“We don’t have a clear answer,” Sekine said. “But it is now more clear that the key question is which is more important:  the chemistry of the water or the duration of its presence?”

And the way to address the question, he said, is through a mix of planetary science and environmental science.

“This is a first step in the application of environmental chemistry to Mars,” Sekine said.… Read more

Icy Moons and Their Plumes

The existence of water or water vapor plumes on Europa has been studied for years, with a consensus view that they do indeed exist.  Now NASA scientists have their best evidence so far that the moon does sporadically send water vapor into its atmosphere.  (NASA/ESA/K. Retherford/SWRI)

Just about everything that scientists see as essential for extraterrestrial life — carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur and sources of energy — is now known to be pretty common in our solar system and beyond.  It’s basically there for the taking  by untold potential forms of life.

But what is not at all common is liquid water.  Without liquid water Earth might well be uninhabited and today’s Mars, which was long ago significantly wetter, warmer and demonstrably habitable,  is widely believed to be uninhabited because of the apparent absence of surface water (and all that deadly radiation, too.)

This is a major reason why the discovery of regular plumes of water vapor coming out of the southern pole of Saturn’s moon Enceladus has been hailed as such a promising scientific development.  The moon is pretty small, but most scientists are convinced it does have an under-ice global ocean that feeds the plume and just might support biology that could be collected during a flyby.

But the moon of greatest scientific interest is Europa, one of the largest that orbits Jupiter.  It is now confidently described as having a sub-surface ocean below its crust of ice and — going back to science fiction writer extraordinaire Arthur C. Clarke — has often been rated the most likely body in our solar system to harbor extraterrestrial life.

That is why it is so important that years of studying Europa for watery plumes has now paid off.   While earlier observations strongly suggested that sporadic plumes of water vapor were in the atmosphere, only last month was the finding nailed, as reported in the journal Nature Astronomy.

“While scientists have not yet detected liquid water directly, we’ve found the next best thing: water in vapor form,” said Lucas Paganini, a NASA planetary scientist who led the water detection investigation.

 

As this cutaway shows, vents in Europa’s icy crust could allow plumes of water vapor to escape from a sub-surface ocean. If observed up close, the chemical components of the plumes would be identified and could help explain the nature and history of the ocean below. ( NASA) 

The amount of water vapor found in the European atmosphere wasn’t great — about an Olympic-sized pool worth of H2O.  … Read more

Mapping Titan, the Most Earth-Like Body in Our Solar System

In an image created by NASA’s Cassini spacecraft, sunlight reflects off lakes of liquid methane around Titan’s north pole.  Cassini radar and visible-light images allowed researchers to put together the first global geological map of Saturn’s largest moon.  (NASA/JPL-Caltech/University of Arizona/University of Idaho)

Saturn’s moon Titan has lakes and rivers of liquid hydrocarbons, temperatures that hover around -300 degrees Fahrenheit, and a thick haze that surrounds it and has cloaked it in mystery.   An unusual place for sure, but perhaps what’s most unusual is that Titan more closely resembles Earth of all the planets and moons in our solar system.

This is because like only Earth it has that flowing liquid on its surface, it has a climate featuring wind and rain that form dunes, rivers, lakes, deltas and seas (probably of filled with liquid methane and ethane), it has a thick atmosphere and it has weather patterns that change with the seasons.  The moon’s methane cycle is quite similar to our water cycle.

And now astronomers have used data from NASA’s Cassini-Huygens mission to map the entire surface of Titan for the first time.  Their work has found a global terrain of mountains, plains, valleys, craters and lakes .  Again, this makes Titan unlike anywhere else in the solar system other than Earth.

“Titan has an atmosphere like Earth. It has wind, it has rain, it has mountains,” said Rosaly Lopes, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena.  She and her colleagues wove together images and radar measurements taken by the spacecraft to produce the first global map of the moon.

“Titan has an active methane-based hydrologic cycle that has shaped a complex geologic landscape, making its surface one of most geologically diverse in the solar system,” she said.  “It’s a really very interesting world, and one of the best places in the solar system to look for life,”

Cassini orbited Saturn from 2004 to 2017 and collected vast amounts of information about the ringed gas giant and its moons. The mission included more than 100 fly-bys of Titan,  which allowed researchers to study the moon’s surface through its thick atmosphere and survey its terrain in unprecedented detail.

The first global geologic map of Titan is based on radar and visible-light images from NASA’s Cassini mission.

Their work, which now adds the surface of Titan to the kind of geological mapping done of the surfaces of Mars, Mercury and our moon, was published in Nature Astronomy.Read more

PIXL: A New NASA Instrument For Ferreting Out Clues of Ancient Life on Mars

 

Extremely high definition images of the com ponents of rocks and mud as taken by PIXL, the Planetary Instrument for X-ray Lithochemistry .   On the Mars 2020 rover, PIXL  will have significantly greater capabilities than previous similar instruments sent to Mars.  Rather than reporting bulk compositions averaged over several square centimeters, it will identify precisely where in the rock each element resides. With spatial resolution of about 300 micrometers, PIXL will conduct the first ever petrology investigations on Mars, correlating elemental compositions with visible rock textures . (NASA)J

The search for life, or signs of past life beyond Earth is now a central issue in space science, is central to the mission of NASA, and is actually a potentially breakthrough discovery in the making  for humanity.    The scientific stakes could hardly be higher.

But identifying evidence of ancient microbial life – and refuting all reasonable non-biological explanations for that evidence — is stunningly difficult.

As recent wrangling over Earth’s oldest rocks in Greenland has shown, determining the provenance of a deep-time biosignature even here on Earth is extraordinarily difficult. In 2016, scientists reported discovery of 3,700 million yr-old stromatolites in the Isua geological area of Greenland.

Just three years later, a field workshop held at the Isua discovery site brought experts from around the world to examine the intriguing structures and see whether the evidence cleared the very high bar needed to accept a biological interpretation. While the scientists who published the initial discovery held their ground, not one of the other scientists felt convinced by the evidence before them.  Watching and listening as the different scientists presented their cases was a tutorial in the innumerable factors involved in coming to any conclusion.

Now think about trying to wrestle with similar or more complex issues on Mars, of how scientists can reach of level of confidence to report that a sign (or hint) of past life has apparently been found.

As it turns out, the woman who led the Greenland expedition — Abigail Allwood of NASA’s Jet Propulsion Lab — is also one of the key players in the upcoming effort to find biosignatures on Mars.  She is the principal investigator of the Planetary Instrument for X-ray Lithochemistry (PIXL) that will sit on the extendable arm of the rover, and it has capabilities to see in detail the composition of Mars samples as never before.

The instrument has, of course, been rigorously tested to understand what it can and cannot do. … Read more

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