Category: Our World (page 1 of 5)

Surprising Insights Into the Asteroid Bennu’s Past, as OSIRIS-REx Prepares For a Sample-Collecting “Tag”

Artist rendering of the OSIRIS-REx spacecraft as it will approach the asteroid Bennu to collect a sample of ancient, pristine solar system material. The  pick-up”tag” is scheduled for Oct. 20. (NASA Goddard Space Flight Center, University of Arizona)

Long before there was an Earth, asteroids large and small were orbiting our young sun.  Among them was one far enough out from the sun to contain water ice, as well as organic compounds with lots of carbon.  In its five billion years or so as an object,  the asteroid was hit and broken apart by other larger asteroids, probably grew some more as smaller asteroids hit it,  and then was smashed to bits again many millions of years ago.  Some of it might have even landed on Earth.

The product of this tumultuous early history is the asteroid now called Bennu, and the destination for NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) mission.  On October 20, the spacecraft will make its dramatic final descent, will touch the ground long enough to collect some samples of the surface, and then will in the months ahead return home with its prized catch.

The sample will consist of grains of a surface that have experienced none of the ever-active geology on Earth,  no modifications caused by life,  and little of the erosion and weathering.  In other words, it will be a sample of the very early solar system from which our planet arose.

“This will be our first chance to look at an ancient, carbon-rich environment – the most pristine example of the chemistry of the very early solar system,” said Daniel Glavin, an astrobiologist at NASA’s Space Flight Center and a co-investigator of the OSIRIS-REx team.  “Anything as ancient on early Earth would have been modified many times over.”

“But at Bennu we’ll see the solar system, and the Earth,  as it was chemically before all those changes took place.  This will be the kind of pristine pre-biotic chemistry that life emerged from.”

This image of Bennu was taken by the OSIRIS-REx spacecraft from a distance of around 50 miles (80 km).
(NASA/Goddard/University of Arizona)

Bennu is an unusual asteroid.  It orbits relatively close to Earth — rather than in the main asteroid belt between Mars and Jupiter — and that’s one of several main reasons why it was selected for a visit.  It is also an asteroid with significant amounts of primeval carbon and organics, which is gold for scientists eager to understand the early solar system, planet formation and the origin of life on Earth.… Read more

An “Elegant” New Theory on How Earth Became a Wet Planet

About 71 percent of the Earth’s surface is covered by water, and vast quantities of water are also locked up in minerals on and beneath the surface.  This image of Earth comes from NASA’s Earth Polychromatic Imaging Camera (EPIC) on NOAA’s Deep Space Climate Observatory (DSCOVR), orbits Earth from a distance of about 1 million miles away. (NASA)

One of the enduring puzzles of our planet is why it is so wet.

Since Earth formed relatively close to the sun,  planetary scientists have generally held that any of the water in the building blocks of early-forming Earth was baked out and so was unavailable to make oceans or our atmosphere.

That led to theories explaining the oceans and wet atmosphere of Earth as a later addition, brought to us by meteorites and comets formed beyond the solar system’s so-called “snow line,” where volatile compounds such as water can begin to condense into ice.

This snow line is a general area between Mars and Jupiter, and that means under this theory that our water would have had to come from awfully far away.   Further complicating this view is that the isotopic makeup of that distant water ice is somewhat different from much of the water on Earth.

Now, a new paper in the journal Science from Laurette Piani of  the Université de Lorraine and colleagues, argues that Earth’s water was simply acquired like most other of our materials, through accretion when the planet formed in the inner solar nebula.

To reach that conclusion, the group re-examined 13 meteorites of the parched type formed between Earth and the sun, and they found more than of enough hydrogen present to explain how Earth got so wet (wet for our solar system, that is.)

In fact, they extrapolated from their data that enough water was available in the nebular cloud  that accompanied the formation of our sun and formed those early meteorites — called enstatite chondrites — to create three times as much water as our oceans hold.

 

 

New measurements of enstatite chondrites indicate that water could have been primarily acquired from Earth’s building blocks. Additional water was delivered to Earth’s early oceans and atmosphere by water-rich material from comets and the outer asteroid belt. (Science)

“Our discovery shows that the Earth’s building blocks might have significantly contributed to the Earth’s water and that hydrogen bearing material was present in the inner solar system at the time of the Earth and rocky planet formation, even though the temperatures were too high for water to condense,'” Piani told me.… Read more

Cores, Planets and The Mission to Psyche

The asteroid Psyche will be the first metal-rich celestial body to be visited by a spacecraft.  The NASA mission launches in 2022 and is expected to arrive at the asteroid in late 2026.  A central question to be answered is whether Psyche is the exposed  core of a protoplanet that was stripped of its rocky mantle. (NASA)

Deep inside the rocky planets of our solar system, as well as some solar system moons,  is an iron-based core.

Some, such as Earth’s core,  have an inner solid phase and outer molten phase, but the solar system cores studied so far are of significantly varied sizes and contain a pretty wide variety of elements alongside the iron.  Mercury, for instance, is 85 percent core by volume and made up largely of iron, while our moon’s core is thought to be 20 percent of its volume and is mostly iron with some sulfur and nickel.

Iron cores like our own play a central role in creating a magnetic field around the planet, which in turn holds in the atmosphere and may well be essential to make a planet habitable.  They are also key to understanding how planets form after a star is forged and remaining dense gases and dust are kicked out to form a protoplanetary disk, where planets are assembled.

So cores are central to planetary science, and yet they are obviously hard to study.  The Earth’s core starts about 1,800 miles below the surface, and the cores of gas giants such as Jupiter are much further inward, and even their elemental makeups are not fully understood.

All this helps explains why the upcoming NASA mission to the asteroid Psyche is being eagerly anticipated, especially by scientists who focus on planetary formation.

Scheduled to launch in 2022, the spacecraft will travel to the main asteroid belt between Mars and Jupiter and home in on what has been described as an unusual “metal body,”  which is also one of the largest asteroids orbiting the sun.

While some uncertainty remains,  it appears that Psyche is the  exposed nickel-iron core of a long-ago emerging rocky protoplanet, with the rest of the planet stripped away by collisions billions of years ago.

An artist’s impression of solar system formation, and the formation of a protoplanetary disk filled with gases and dust that over time clump together and smash into each other to form larger and larger bodies. (Gemini Observatory/AURA artwork by Lynette Cook )

That makes Psyche a most interesting place to visit.… Read more

Thinking About Life (or Lyfe) Through The Prism of “Star Trek”

This column was written for Many Worlds by Michael L. Wong and Stuart Bartlett.  Wong is a postdoctoral research associate at the University of Washington’s Astronomy and Astrobiology program and is a member of  NASA’s Nexus for Exoplanet System Science (NExSS) initiative as part of the university’s Virtual Planetary Laboratory team.  Bartlett is a postdoctoral scholar in Geochemistry at the California Institute of Technology and has been a fellow at the Earth-Live Science Institute (ELSI) in Tokyo.

 

Spock communicates with a Horta,  a fictional silicon-based life form composed of molten rock and acid.  (Star Trek; CBS Studios)

By Michael L. Wong and Stuart Bartlett

 

The search for extraterrestrial life is in its early phase still  and, the truth is, we don’t yet know if life exists beyond our pale blue dot.  Or, if it does, whether it will be easily recognizable or truly bizarre.

Predicting what might be out there, and how to find it, is a hypothesis-driven area of research at present — one that has given rise to hundreds of possible definitions for the “life” we are looking for.

But after grounding ourselves in scientific principles, it may be that our greatest tool is to let our imaginations fly. Science fiction often helps us embrace our ignorance of what might be out there.

In the Star Trek universe, our galaxy is teeming with life—both astonishingly familiar and incredibly different.

The familiar variety includes Mr. Spock, the U.S.S. Enterprise’s half-human, half-Vulcan science officer. He is the product of an extraordinary cosmic coincidence: the emergence of nearly identical biochemical machinery on two completely separate worlds. Vulcans—despite their pointy ears, upswept eyebrows, and a nearly religious devotion to bowl cuts—are incredibly similar to humans on the cellular, genetic, and metabolic level.

We can share meals, share air, and, yes, share intimacy. Even their green, copper-based blood is not as alien as it might seem; this trait is typical of most mollusks and crustaceans on Earth.

 

The Crystalline entity was a powerful, spaceborne creature characterized by a crystalline structure that resembled a large snowflake. (Star Trek;  CBS Studios)

But Star Trek also depicts life forms that are incredibly dissimilar from you, me, or Mr. Spock.

Take the Horta, for example. This lumpy mass, like a misshapen meatball crossed with a child’s volcano science experiment, is a silicon-based life form composed of molten rock and acid.

Then there’s Q, a non-corporeal being that possesses god-like powers which, it seems, are directed solely upon harassing Captain Jean-Luc Picard.… Read more

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

What, Exactly, Is A Virus?

An illustration of the coronavirus. (Centers of Disease Control)

By now, the coronavirus is an all too familiar menace to most of the peoples of the world.  How it is spread,  the symptoms of the disease,  the absolute necessity of taking precautions against it — most people know something about the coronavirus pandemic.

But the question of what a virus actually is, what are its characteristics and where do they come from,  this seem to be far less well understood by the public.

So here is a primer on this often so destructive agent and its provenance — a look into the complicated, sometimes deadly and yes, fascinating world of viruses.

Viruses are microscopic pathogens that have genetic material (DNA or RNA molecules that encode the structure of the proteins by which the virus acts), that have a  a protein coat (which surrounds and protects the genetic material), and in some cases they have an outside envelope of lipids.

Most virus species have virions — the name given to a virus when it is not inside a host cell. They are too small to be seen with an optical microscope because they are one hundredth the size of most bacteria.

Transmission electron microscope image shows SARS-CoV-2, the virus that causes COVID-19, isolated from a patient in the U.S. Virus particles are emerging from the surface of cells cultured in the lab. The spikes on the outer edge of the virus particles give coronaviruses their name, crown-like. (NIAID-RML)

Unlike bacteria, viruses are generally not considered to be “alive.”

Although viruses do have genomes, they need to take over the machinery of other living cells to follow their own genome instructions.  This is why viruses cannot reproduce by themselves — as opposed to non-viral parasites  that can reproduce outside of a host cell.

Viruses are also too small and simple to collect and use energy, i.e., perform metabolism.   So they just take energy from the cells they infect, and use it only when they make copies of themselves.  They don’t need any energy at all when they are outside of a cell.

And viruses have no way to control their internal environment,  and so they do not maintain their own homeostasis as living creatures do.

These limitations are what lead many scientists to describe viruses as “almost alive,” which is a complicated state of existence indeed.

 

Infectious particles of an avian influenza virus emerge from a cell. 

Read more

Tales From the Deep Earth

Cross section of the varying layers of the Earth .  (Yuri Arcurs via Getty images)

When especially interesting new planets are discovered in the cosmos, scientists around the world begin the process of identifying their characteristics — their orbit, their mass and density,  their composition, their thermal properties and much more.  It’s all part of a drive that seems to be innate in humans to learn about the workings of the world (or worlds) around us.

This began millennia ago when our distant ancestors started to learn about the make-up and processes of Earth.   We now know enormous amounts about our planet, but I was recently introduced to a domain where our knowledge has some substantial holes.  The area of the Earth least well understood is, not surprisingly, what lies deep below us, in the mantle — the inner 2,900 kilometers (2000 miles) of the planet between the outer crust and the iron core.

The on-going exploration of this vast region — made up substances including some which cannot remain intact on the Earth’s surface — struck me as in some ways comparable to the study of exoplanets.   It’s also a realm where scientific observation is limited, but what knowledge is gained then leads through induction, deduction, modeling and exacting lab work to a gradual expansion back of our knowledge.

And in the case of some high-temperature, high-pressure minerals, this has led to a most unusual technique for identifying and naming key components of our inner planet.  Unable to reach or preserve some of the most important components of the mantle,  geochemists and other deep Earth scientists go to incoming meteorites to learn about what’s beneath (deeply beneath, that is) our feet.

With this in mind, here is a look at the discovery and recent naming of the mineral hiroseite, an unusual but quite widespread component of the very deep Earth.

 

ELSI director Kei Hirose has been honored for his pioneering work in identifying and describing components of the Earth’s lower mantle. In recognition of his work, a newly identified lower mantle mineral has been given the name of hiroseite. (Nerissa Escanlar)

 

It was two decades ago when Kei Hirose – a Japanese geochemist expert in high-pressure, deep-Earth phenomena, then at the Tokyo Institute of Technology – began researching a long-standing problem in understanding the working of the lower depths of our planet’s enormous mantle: the last 300 kilomiles above the boundary with the scalding iron core.

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

On The Rugged Frontier Of The Hunt For Signs Of Life On Early Earth And Ancient Mars

The vigorously debated finding from the Isua greenstone or supercrustal belt, a 1,200-square-mile area of ancient rocks in Greenland.  Proponents say the rises, from .4 to 1.6 inches tall, are  biosignatures of bacteria and sediment mounds that made up stromatolites almost 3.8 billion years ago.  Critics say additional testing has shown they are the result of non-biological forces.  (Nature and Nutman et al.)

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 contains some of the oldest known rocks and outcrops in the world, and 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.  The paper concluded the outcrop had no signs of early life at all.

Debates and disputes are common in geology as the samples get older,  and especially in high profile science with important implications.  In this case, the implications of what is in the rocks reach into the solar system and the cosmos. … Read more

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