Category: The Origin of Life (page 1 of 4)

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

On the Ground in Greenland, at the Disputed Ancient Stromatolite Site

Enlarge to full screen on lower right. A pioneering three-dimensional, virtual reality look at a Greenland outcrop earlier described as containing 3.7-billion- year-old stromatolite fossils, which would be the oldest remnant of life on Earth. The video capture, including the drone-assisted overview of the site, is part of a much larger virtual reality effort to document the setting undertaken late in August. As the video focuses in on the scientifically controversial outcrop, cuts are visible in the smooth surfaces that were made by two teams studying the rocks in great detail to determine whether the reported stromatolite fossils are actually present. (Parker Abercrombie, NASA/JPL and Ian Burch, Queensland University of Technology.)

 

Seldom does one rock outcrop get so many visitors in a day, especially when that outcrop is located in rugged, frigid terrain abutting the Greenland Ice Sheet and can be reached only by helicopter.

But this has been a specimen of great importance and notoriety since it appeared from beneath the snow pack some eight years ago. That’s when it was first identified by two startled geologists as something very different from what they had seen in four decades of scouring the geologically revelatory region – the gnarled Isua supercrustal belt – for fossil signs of very early life.

Since that discovery the rock outcrop has been featured in a top journal and later throughout the world as potentially containing the earliest signature of life on Earth – the outlines of half inch to almost two inch-high stromatolite structures between 3.7 and 3.8 billion years old.

The Isua greenstone, or supracrustal belt, which contains some of the oldest known rocks and outcrops in the world, is about 100 miles northeast of the capital, Nuuk.

If Earth could support the life needed to form primitive but hardly uncomplicated stromatolites that close to the initial cooling of the planet, then the emergence of life might not be so excruciatingly complex after all. Maybe if the conditions are at all conducive for life on a planet (early Mars comes quickly to mind) then life will probably appear.

Extraordinary claims in science, however, require extraordinary proof, and inevitably other scientists will want to test the claims.

Within two years of that initial ancient stromatolite splash in a Nature paper (led by veteran geologist Allen Nutman of the University of Wollongong in Australia), the same journal published a study that disputed many of the key observations and conclusions of the once-hailed ancient stromatolite discovery. … Read more

Exploring Early Earth by Using DNA As A Fossil

Betül Kaçar is an assistant professor at the University of Arizona, and a pioneer in the field of paleogenomics — using genetic material to dive back deep into the ancestry of important compounds. (University of Arizona)

Paleontology has for centuries worked to understand the distant past by digging up fossilized remains and analyzing how and why they fit into the evolutionary picture.  The results have been impressive.

But they have been limited.  The evolutionary picture painted relies largely on the discovery of once hard-bodied organisms, with a smattering of iconic finds of soft-bodied creatures.

In recent years, however, a new approach to understanding the biological evolution of life has evolved under the umbrella discipline of paleogenomics.  The emerging field explores ancient life and ancient Earth by focusing on genetic material from ancient organisms preserved in today’s organisms.

These genes can be studied on their own or can be synthetically placed into today’s living organisms to see if, and how, they change behavior.

The goals are ambitious:  To help understand both the early evolution and even the origins of life, as well as to provide a base of knowledge about likely characteristics of potential life on other planets or moons.

“What we do is treat DNA as a fossil, a vehicle to travel back in time,” said Betül Kaçar, an assistant professor at the University of Arizona with more than a decade of experience in the field, often sponsored by the NASA Astrobiology Program and the John Templeton Foundation.  “We build on modern biology, the existing genes, and use what we know from them to construct a molecular tree of life and come up with the ancestral genes of currently existing proteins.”

And then they ask the question of whether and how the expression of those genes — all important biomolecules generally involved in allowing a cell to operate smoothly — has changed over the eons.  It’s a variation on one the basic questions of evolution:  If the film of life were replayed from very early days, would it come out the same?

Cyanobacteria, which was responsible for the build-up of oxygen in the Earth’s atmosphere and the subsequent Great Oxidation Event about 2.5 billion years ago.  Kaçar studies and replaces key enzymes in the cyanobacteria in her effort to learn how those ancestral proteins may have behaved when compared to the same molecules today.

The possibility of such research — of taking what is existing today and reconstructing ancient sequences from it — was first proposed by Emile Zuckerkandl, a biologist known for his work in the 1960s with Linus Pauling on the hypothesis of the “molecular clock.”… Read more

“Agnostic Biosignatures,” And the Path to Life as We Don’t Know It

Most research into signs of life in our solar system or on distant planets uses life on Earth as a starting point. But now NASA has begun a major project to explore the potential signs of life very different from what we have on Earth.  For example, groups of molecules, like those above, can be analyzed for complexity, regardless of their specific chemical constituents.  ( Brittany Klein/Goddard Space Flight Center)

Biosignatures – evidence that says or suggests that life has been present – are often very hard to find and interpret.

Scientists examining fossilized life on Earth can generally reach some sort of agreement about what is before them, but what about the soft-bodied or even single-celled organisms that were the sum total of life on Earth for much of the planet’s history as a living domain? Scientific disagreements are common.

Now think of trying to determine whether a particular outline on an ancient Martian rock, or a geochemical or surface anomaly on that rock, is a sign of life. Or perhaps an unexpected abundance of a particular compound in one of the water vapor plumes coming out of the moons Europa or Enceladus. Or a peculiar chemical imbalance in the atmosphere of a distant exoplanet as measured in the spectral signature collected via telescope.

These are long-standing issues and challenges, but they have taken on a greater urgency of late as NASA missions  (and those of other space agencies around the world) are being designed to actively look for signs of extraterrestrial life – most likely very simple life – past or present.

And that combination of increased urgency and great difficulty has given rise to at least one new way of thinking about those potential signs of life. Scientists call them “agnostic biosignatures” and they do not presuppose any particular biochemistry.

“The more we explore the solar system and distant exoplanets, the more we find worlds that are really foreign,”  said Sarah Stewart Johnson, at an assistant professor at Georgetown University and principal investigator of the newly-formed Laboratory for Agnostic Biosignatures (LAB).  The LAB team won a five-year, $7 million grant last year from NASA’s Astrobiology Program.

“So our goal is to go beyond our current understandings and find ways to explore the world of life as we don’t know it,” she told me.  “That might mean thinking about a spectrum of how ‘alive’ something might be… And we’re embracing uncertainty, looking as much for biohints as biosignatures.”… Read more

Hayabusa2 Snatches Second Asteroid Sample

Artist impression of the Hayabusa2 spacecraft touching down on asteroid Ryugu (JAXA / Akihiro Ikeshita)

“1… 2… 3… 4…”

The counting in the Hayabusa2 control room at the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Sciences (JAXA, ISAS) took on a rhythmic beat as everyone in the room took up the chant, their eyes fixed on the large display mounted on one wall.

“10… 11… 12… 13…”

The display showed the line-of-sight velocity (speed away from or towards the Earth) of the Hayabusa2 spacecraft. The spacecraft was about 240,000,000 km from the Earth where it was studying a near-Earth asteroid known as Ryugu. At this moment, the spacecraft was dropping to the asteroid surface to collect a sample of the rocky body.

“20… 21… 22… 23…”

Asteroid Ryugu from an altitude of 6km. Image was captured with the Optical Navigation Camera – Telescopic (ONC-T) on July 20, 2018 ( JAXA, University of Tokyo & collaborators)

Asteroid Ryugu is a carbonaceous or “C-type” asteroid; a class of small celestial bodies thought to contain organic material and undergone relatively little alteration since the beginning of the Solar System. Rocks similar to Ryugu would have pelted the early Earth, possibly delivering both water and the first ingredients for life to our young planet. Where and when these asteroids formed and how they moved through the Solar System is therefore a question of paramount importance to understanding how terrestrial planets like the Earth became habitable. It is a question not only tied to our own existence, but also to assessing the prospect of life elsewhere in the Universe.

The Hayabusa2 mission arrived at asteroid Ryugu just over one year ago at the end of June 2018. The spacecraft remotely analyzed the asteroid and deployed two rovers and a lander to explore the surface. Then in February of this year, the spacecraft performed its own descent to touchdown and collect a sample. The material gathered will be analyzed back on Earth when the spacecraft returns home at the end of 2020.

Touchdown is one of the most dangerous operation in the mission. The distances involved mean that it took about 19 minutes to communicate with the spacecraft during the first touchdown and 13 minutes during the second touchdown, when the asteroid had moved slightly closer to Earth. Both these durations are too long to manually guide the spacecraft to the asteroid surface.… Read more

NASA Announces Astrobiology Mission to Titan

 

The Dragonfly drone has been selected as the next New Frontiers mission, this time to Saturn’s moon Titan.  Animation of the vehicle taking off from the surface of the moon. (NASA)

A vehicle that flies like a drone and will try to unravel some of the mysteries of Saturn’s moon Titan was selected yesterday to be the next New Frontiers mission to explore the solar system.

Searching for the building blocks of life,  the Dragonfly mission will be able to fly multiple sorties to sample and examine sites around Saturn’s icy moon.

Titan has a thick atmosphere and features a variety of hydrocarbons, with rivers and lakes of methane, ethane and natural gas, as well as and precipitation cycles like on Earth.  As a result, Dragonfly has been described as an astrobiology mission because it will search for signs of the prebiotic environments like those on Earth that gave rise to life.

“Titan is unlike any other place in the solar system, and Dragonfly is like no other mission,” said Thomas Zurbuchen, NASA’s associate administrator for science at the agency headquarters in Washington.

“It’s remarkable to think of this rotorcraft flying miles and miles across the organic sand dunes of Saturn’s largest moon, exploring the processes that shape this extraordinary environment. Dragonfly will visit a world filled with a wide variety of organic compounds, which are the building blocks of life and could teach us about the origin of life itself.”

 

Saturn’s moon Titan is significantly larger than our moon, and larger than the planet Mercury. It features river channels of ethane and methane, and lakes of liquified natural gas. It is the only other celestial body in our solar system that has flowing liquid on its surface. (NASA)

As described in a NASA release, Titan is an analog to the very early Earth, and can provide clues to how life may have arisen on our planet.

Dragonfly will explore environments ranging from organic dunes to the floor of an impact crater where liquid water and complex organic materials key to life once existed together for possibly tens of thousands of years. Its instruments will study how far prebiotic chemistry may have progressed.

They also will investigate the moon’s atmospheric and surface properties and its subsurface ocean and liquid reservoirs. Additionally, instruments will search for chemical evidence of past or extant life.

Because it is so far from the sun, Titan’s surface temperature is around -290 degrees Fahrenheit and its surface pressure is 50 percent higher than Earth’s.… Read more

The Message of Really, Really Extreme Life

Hydrothermal system at Ethiopia’s Danakil Depression, where uniquely extreme life has been found in salt chimneys and surrounding water. The yellow deposits are a variety of sulphates and the red areas are deposits of iron oxides. Copper salts color the water green. (Felipe Gomez/Europlanet 2020 RI)

Ethiopia’s Dallol volcano and hot springs have created an environment about as hostile to life as can be imagined.

Temperatures in the supersaturated water reach more than 200 degrees F (94 C) and are reported to approach pure acidity, with an extraordinarily low pH of  0.25.  The environment is also highly salty, with salt chimneys common.

Yet researchers have just reported finding ultra-small bacteria living in one of the acidic, super-hot salt chimneys.  The bacteria are tiny — up to 20 times smaller than the average bacteria — but they are alive and in their own way thriving.

In the world of extremophiles, these nanohaloarchaeles order bacteria are certainly on the very edge of comprehension.  But much the same can be said of organisms that can withstand massive doses of radiation, that survive deep below the Earth’s surface with no hint of life support from the sun and its creations, that keep alive deep in glacier ice and even floating high in the atmosphere.  And as we know, spacecraft have to be well sterilized because bacteria (in hibernation) aboard can survive the trip to the moon or Mars.

Not life it is generally understood.  But the myriad extremophiles found around the globe in recent decades have brought home the reality that we really don’t know where and how life can survive;  indeed, these extremophiles often need their conditions to be super-severe to succeed.

And that’s what makes them so important for the search for life beyond Earth.  They are proof of concept that some life may well need planetary and atmospheric conditions that would have been considered utterly uninhabitable not long ago.

 

Montage from the Dallol site: (A) the sampling site, (B) the small chimneys (temperature of water 90 ºC. (C) D9 sample from a small chimney in (A). (D-L) Scanning Electron Microscope and (M-O) Scanning Transmission Electron Microscope images of sample D9 showing the morphologies of ultra-small microorganisms entombed in the mineral layers. (Gomez et al/Europlanet 2020 Research Infrastructure)

The unusual and extreme life and geochemistry of Dallol has been studied by a team led by Felipe Gómez from Astrobiology Center in Spain.… Read more

Starting Life on Another Planet

Inside the planet simulator at McMaster University
A look inside the planet simulator in the Origins of Life laboratory at McMaster University. Within this chamber, the origins of life can be explored on different worlds (McMaster University).

Have you ever wondered if you could kick-start life on another planet? In the Origins of Life laboratory at McMaster University in Canada, there is a machine that allows you to try this very task.

Exactly how life began on the Earth remains heavily debated, but one of the most famous ideas was proposed by Charles Darwin in a letter to a friend in 1871:

“But if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts…” Darwin began.

In contrast to the vast ocean, a pond would allow simple organic molecules to be concentrated and increase the probability of reactions that would form chains of longer molecules such as RNA; a single-stranded version of DNA that is thought to have been used for genetic information by the earliest forms of life.

warm little pond
Did life begin in warm little ponds such as these? (Katharine Sutliff / Science).

It is highly likely that such warm little ponds would have the necessary ingredients to build such complex molecules. Experiments performed by Stanley Miller and Harold Urey in the 1950s demonstrated that water containing just the basic molecules of methane, ammonia and hydrogen would react to form a wide range of simple organics. Meteorites have also been found to contain similar molecules, proposing an alternative way of populating pools of water on the early Earth.

These ponds should therefore contain plenty of simple organics such as nucleotides, which stack together to form RNA. However, this stacking step turns out to be tricky.

“Anywhere where you have stagnant water and take sample, you will find organic molecules,” explains Maikel Rheinstädter, associate director of McMaster’s Origins Institute. “But you only find the building blocks, not the longer chains. Obviously, something is missing.”

In pond water, molecules are free to move around and potentially meet to initiate a reaction. The problem is that nucleotides carry a negative charge which repels the molecules from one another. While their motion is unconstrained, the nucleotides will therefore not approach close enough to react and form a longer molecule.

The solution is to dry out the pond.

As winter turned to summer on our young planet, shallow pools would have evaporated to leave the molecules suspended in the water lying on the muddy clay bottom.… Read more

NExSS 2.0

Finding new worlds can be an individual effort, a team effort, an institutional effort. The same can be said for characterizing exoplanets and understanding how they are affected by their suns and other planets in their solar systems. When it comes to the search for possible life on exoplanets, the questions and challenges are too great for anything but a community. NASA’s NExSS initiative has been an effort to help organize, cross-fertilize and promote that community. This artist’s concept Kepler-47, the first two-star systems with multiple planets orbiting the two suns, suggests just how difficult the road ahead will be. ( NASA/JPL-Caltech/T. Pyle)

 

The Nexus for Exoplanet System Science, or “NExSS,”  began four years ago as a NASA initiative to bring together a wide range of scientists involved generally in the search for life on planets outside our solar system.

With teams from seventeen academic and NASA centers, NExSS was founded on the conviction that this search needed scientists from a range of disciplines working in collaboration to address the basic questions of the fast-growing field.

Among the key goals:  to investigate just how different, or how similar, different exoplanets are from each other; to determine what components are present on particular exoplanets and especially in their atmospheres (if they have one);  to learn how the stars and neighboring exoplanets interact to support (or not support) the potential of life;  to better understand how the initial formation of planets affects habitability, and what role climate plays as well.

Then there’s the  question that all the others feed in to:  what might scientists look for in terms of signatures of life on distant planets?

Not questions that can be answered alone by the often “stove-piped” science disciplines — where a scientist knows his or her astrophysics or geology or geochemistry very well, but is uncomfortable and unschooled in how other disciplines might be essential to understanding the big questions of exoplanets.

 

The original NExSS team was selected from groups that had won NASA grants and might want to collaborate with other scientists with overlapping interests and goals  but often from different disciplines. (NASA)

The original idea for this kind of interdisciplinary group came out of NASA’s Astrobiology Program, and especially from NASA astrobiology director Mary Voytek and colleague Shawn Domogal-Goldman of the Goddard Space Flight Center, as well as Doug Hudgins of NASA Astrophysics.  It was something of a gamble, since scientists who joined would essentially volunteer their time and work and would be asked to collaborate with other scientists in often new ways.… Read more

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