Category: The Origin of Life (page 1 of 3)

“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.”

Johnson first visited the acid salt lakes of the Yilgarn Craton of Western Australia as a graduate student at MIT, and has returned multiple with colleagues to understand mineral biosignatures as well as biomarker preservation in this analog environment for early Mars.

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

A New and Revelatory Window Into Evolution on Earth

A Leanchoilia fossil from at the Qingjiang site in China. A very early arthropod  found with sharply defined appendages is an arthropod and  one of the prime examples of early Cambrian life (D Fu et al., Science 363:1338 (2019)

Virtually every definition of the word “life” includes the capability to undergo Darwinian evolution as a necessary characteristic.  This is true of life on Earth and of thinking about what would constitute life beyond Earth.  If it can’t change, the thinking goes, then it cannot be truly alive.

In addition, evolutionary selection and change occurs within the context of broad planetary systems — the chemical makeup of the atmosphere, the climactic conditions, the geochemistry and more.  If an environment is changing, then the lifeforms that can best adapt to the new conditions are the ones that will survive and prosper.

So evolution is very much part of the landscape that Many Worlds explores — the search for life beyond Earth and effort to understand how life emerged on Earth.  Evolution happens in the context of broad conditions on Earth (and perhaps elsewhere), and finding potential life elsewhere involves understanding the conditions on distant planets and determining if they are compatible with life.

This all came to mind as I read about the discovery of a remarkable collection of fossils alongside a river in China, fossils of soft-bodied creatures that lived a half billion years ago in the later phase of what is termed the the Cambrian explosion.  They are of being compared already with the iconic “Burgess Shale” fossil find in Canada of decades ago, and may well shed equally revelatory light on a crucial time in the evolution of life on Earth.

Artist rendering of Qingjiang life showing characteristics of different early Cambrian taxonomical groups.  More than 50 percent had never been identified before. (ZH Yao and DJ Fu)

The new discovery is reported in the journal Science in a paper authored by Dongjing Fu and a team largely from the Northwest University in Xi’an.  The paper reports on a zoo of Cambrian-era creatures, with more than half of them never identified before in the rock record.

The animals are soft-bodied — making it all the more remarkable that they were preserved — and some bear little resemblance to anything that followed.   Like the Burgess Shale fossils, the Qingjiang discovery is of an entire ecosystem that largely disappeared as more fit (and predatory) animals emerged.… Read more

Japan’s Hayabusa2 Asteroid Mission Reveals a Remarkable New World

The Hayabusa2 touchdown movie, taken on February 22, 2019 (JST) when Hayabusa2 first touched down on asteroid Ryugu to collect a sample from the surface. It was captured using the onboard small monitor camera (CAM-H). The video playback speed is five times faster than actual time (JAXA).

On March 5 the Japan Aerospace Exploration Agency (JAXA) released the extraordinary video shown above. The sequence of 233 images shows a spacecraft descending to collect material from the surface of an asteroid, before rising amidst fragments of ejected debris. It is an event that has never been captured on camera before.

The images were taken by a camera onboard the Hayabusa2 spacecraft, a mission to explore a C-type asteroid known as “Ryugu” and bring a sample back to Earth.

C-type asteroids are a class of space rock that is thought to contain carbonaceous material and undergone little evolution since the early days of the Solar System. These asteroids may have rained down on the early Earth and delivered our oceans and possibly our first organics. Examination of the structure of Ryugu and its composition compared to Earth will help us understand how planets can become habitable.

Asteroid Ryugu from an altitude of 6km
Asteroid Ryugu from an altitude of 6km. Image was captured with the Optical Navigation Camera – Telescopic (ONC-T) on July 20, 2018 at around 16:00 JST. (JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST.)

Hayabusa2 arrived at asteroid Ryugu on June 27, 2018. The spacecraft spent the summer examining the asteroid with a suite of onboard instruments. Despite being a tiny world at only 1km across, Hayabusa2 spotted different seasons on Ryugu. Like the Earth, the asteroid’s rotation axis is inclined so that different levels of sunlight reach the northern and southern hemispheres.

It also rotated upside down, spinning in the opposite sense to the Earth and its own path around the Sun. This is likely indicative of a violent past, a view supported by the heavily bouldered and cratered surface. This rugged terrain presented the Hayabusa2 team with a problem: where could they land?

After a summer of observations, Hayabusa2 had been planning three different operations on the asteroid surface. The first was the deployment of two little rovers known as the MINERVA-II1. The second was the release of a shoebox-sized laboratory known as MASCOT, designed by the German and French space agencies.… Read more

All About Emergence

A swarm of birds act as an emergent whole as opposed to a collection of individual birds. The workings of swarms have been fruitfully studied by artificial life scientists, who look for abstracted insights into life via computers and other techniques. (Walerian Walawski)

 

If there was a simple meaning of the often-used scientific term “emergence,” then 100-plus scientists wouldn’t have spent four days presenting, debating and not infrequently disagreeing about what it was.

But as last month’s organizers of the Earth-Life Science Institute’s “Comparative Emergence” symposium in Tokyo frequently reminded the participants, those debates and disputes are perfectly fine and to be expected given the very long history and fungibility of the concept.

At the same time, ELSI leaders also clearly thought that the term can have resonance and importance in many domains of science, and that’s why they wanted practitioners to be exposed more deeply to its meanings and powers.

Emergence is a concept commonly used in origins of life research, in complexity and artificial life science; less commonly in chemistry, biology, social and planetary sciences; and — originally – in philosophy. And in the 21st century, it is making a significant comeback as a way to think about many phenomena and processes in the world.

So what is “emergence?” Most simply, it describes the ubiquitous and hugely varied mechanisms by which simple components in nature (or in the virtual or philosophical world) achieve more complexity, and in the process become greater than the sum of all those original parts.

The result is generally novel, often surprising, and sometimes most puzzling – especially since emergent phenomena involve self-organization by the more complex whole.

Think of a collection of ants or bees and how they join leaderless by the many thousands to make something – a beehive, an ant colony – that is entirely different from the individual creatures.

 

The Eagle nebula is an intense region of star formation, an emergent phenomenon
that clearly creates something novel out of simpler parts. (European Space Observatory.)

Think of the combination of hydrogen and oxygen gases which make liquid water. Think of the folding of proteins that makes genetic information transfer possible. Think of the processes by which bits of cosmic dust clump and clump and clump millions of times over and in time become a planetesimal or perhaps a planet. Think of how the firing of the billions of neurons in your brain results in consciousness.Read more

The Moon-Forming Impact And Its Gifts

 

Rice University petrologists have found Earth most likely received the bulk of its carbon, nitrogen and other life-essential volatile elements from the planetary collision that created the moon more than 4.4 billion years ago. (Rice University)

 

The question of how life-essential elements such as carbon, nitrogen and sulfur came to our planet has been long debated and is a clearly important and slippery scientific subject.

Did these volatile elements accrete onto the proto-Earth from the sun’s planetary disk as the planet was being formed?  Did they arrive substantially later via meteorite or comet?  Or was it the cataclysmic moon-forming impact of the proto-Earth and another Mars-sized planet that brought in those essential elements?

Piecing this story together is definitely challenging,  but now there is vigorous support for one hypothesis — that the giant impact brought us the elements would later be used to enable life.

Based on high pressure-temperature experiments, modeling and simulations, a team at Rice University’s Department of Earth, Environmental and Planetary Sciences makes that case in Science Advances for the central role of the proto-planet called Theia.

“From the study of primitive meteorites, scientists have long known that Earth and other rocky planets in the inner solar system are volatile-depleted,” said study co-author Rajdeep Dasgupta. “But the timing and mechanism of volatile delivery has been hotly debated. Ours is the first scenario that can explain the timing and delivery in a way that is consistent with all of the geochemical evidence.”

“What we are saying is that the impactor definitely brought the majority supply of life-essential elements that we see at the mantle and surface today,” Dasgupta wrote in an email.

 

A schematic depicting the formation of a Mars-sized planet (left) and its differentiation into a body with a metallic core and an overlying silicate reservoir. The sulfur-rich core expels carbon, producing silicate with a high carbon to nitrogen ratio. The moon-forming collision of such a planet with the growing Earth (right) can explain Earth’s abundance of both water and major life-essential elements like carbon, nitrogen and sulfur, as well as the geochemical similarity between Earth and the moon. (Rajdeep Dasgupta; background photo of the Milky Way galaxy is by Deepayan Mukhopadhyay)

 

Some of their conclusions are based on the finding of a similarity between the isotopic compositions of nitrogen and hydrogen in lunar glasses and in the bulk silicate portions of the Earth. Read more

« Older posts

© 2019 Many Worlds

Theme by Anders NorenUp ↑