Author: Marc Kaufman (page 1 of 18)

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

How Many Habitable Zone Planets Can Orbit a Host Star?

This representation of the Trappist-1 system shows which planets could potentially have temperature conditions which would allow for the presence of liquid water, seen generally as essential for life.  The inner three planets are likely too hot, and the outer planet is probably too cold, but the middle three planets might be just right. (NASA / JPL-Caltech)

Our solar system has but one planet orbiting in what is commonly known as the habitable zone — at a distance from the host star where water could be liquid at times rather than always ice or gas.  That planet, of course, is Earth.

But from a theoretical, dynamical perspective, does this always have to be the case?  The answer to that question is no because a number of stars are known to have more than one habitable zone planet.

Now a team from the University of California, Riverside has produced a study that concludes as many as seven Earth-sized, habitable zone planets could orbit a single star — if there were no large Jupiter-sized planets in the system and if the star was of a particular type.

The article, published in the Astronomical Journal, concluded that seven habitable zone planets was the maximum for a star, but a sun such as ours could potentially support six planets with sometimes liquid water — a condition considered essential for life.

Study leader Stephen Kane, an astrobiologist who focuses on potentially habitable exoplanets, said he had been studying the nearby solar system Trappist-1, which has three Earth-like planets in its habitable zone and seven planets all together.

“This made me wonder about the maximum number of habitable planets it’s possible for a star to have, and why our star only has one,” Kane said.

With the discovery of an eighth planet, the Kepler-90 system is the first to tie with our solar system in number of planets. Artist’s concept. Credit: NASA/Ames Research Center/Wendy Stenzel

His conclusion:

“Even though (our solar system) only has one planet in the habitable zone, it’s not necessarily the typical situation. A far more typical scenario may be to have many planets in the habitable zone, depending on the presence of a giant planet.”

More later about the destabilizing effects of giant planet, but the Kane (and others) say that looking for solar systems without Jupiter-size planets has become increasingly important because of this effect on other terrestrial planets.

To determine how many habitable zone planets might be possible in a solar system, his team created a model system in which they simulated planets of various sizes orbiting their stars.

Read more

Our Sun, as Never Seen Before

This animation shows a series of views of the sun captured with the Extreme Ultraviolet Imager (EUI) on ESA/NASA’s Solar Orbiter on May 30, 2020. They show the sun’s appearance at a wavelength of 17 nanometers, which is in the extreme ultraviolet region of the electromagnetic spectrum. Images at this wavelength reveal the upper atmosphere of the sun and the corona, which has a temperature of more than a million degrees. Solar Orbiter/EUI Team (ESA & NASA; CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL)

The first images of the sun from the European Space Agency/NASA’s Solar Orbiter have been released and are stupendous.  They are the closest photos ever taken of the star that we orbit, and have already revealed some fascinating features that nobody knew existed.

Launched early this year, the spacecraft completed its first close pass of the sun in mid-June and began sending back images and data.

“These amazing images will help scientists piece together the sun’s atmospheric layers, which is important for understanding how it drives space weather near the Earth and throughout the solar system.” aid Holly Gilbert, NASA project scientist for the mission at NASA’s Goddard Space Flight Center.

The orbiter has already found previously unknown found across the sun miniature versions of the gigantic solar flares that reach out far into space.  But these much smaller versions,  deemed to be “campfires,” are so far seen by not understood.

Normally, the first images from a spacecraft confirm the instruments are working; scientists don’t expect new discoveries from them. But the Extreme Ultraviolet Imager, or EUI, on Solar Orbiter returned data hinting at solar features never observed in such detail.

“The campfires we are talking about here are the little nephews of solar flares, at least a million, perhaps a billion times smaller,” said mission principal investigator David Berghmans an astrophysicist at the Royal Observatory of Belgium said.

“When looking at the new high resolution EUI images, they are literally everywhere we look.”

Solar Orbiter spots ‘campfires’ on the Sun. Locations of campfires are annotated with white arrows.
Solar Orbiter/EUI Team (ESA & NASA; CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL)

That the Solar Orbiter has been able to continue on its mission has been no simple feat.

The coronavirus forced mission control at the European Space Operations Center (ESOC) in Darmstadt, Germany to close down completely for more than a week. During commissioning, the period when each instrument is extensively tested, ESOC staff were reduced to a skeleton crew.… Read more

Sample Return in the Time of Coronavirus

 

Sample return from Mars. Artist rendering of a Mars sample return mission. The mission would use robotic systems and a Mars ascent rocket to collect and send samples of Martian rocks, soils and atmosphere to Earth for detailed chemical and physical analysis.  No rocket has ever taken off from Mars and this NASA and European Space Agency (ESA) project is in early planning stages. Still, blue-ribbon science panels have recommended efforts to begin preparing the public for an eventual Mars sample return. ( Wickman Spacecraft & Propulsion)

For space scientists of all stripes, few goals are as crucial as bringing pieces of Mars, of asteroids, of other planets and moons back to Earth for the kind of intensive study only possible here.  Space missions can, and have, told us many truths about the solar system,  but having a piece of Mars or Europa or an asteroid to study in a lab on Earth is considered the gold standard for learning about the actual composition of other bodies, their histories and whether they could — or once did — harbor life.

In keeping with this ambition, the last National Research Council Decadal Survey listed a Mars “sample return” as the top science priority for large Flagship missions.  And the Perseverance rover that NASA is scheduled to send to Mars next month will — among many other tasks — identify compelling rock samples, collect and cache them so a subsequent mission can pick them up and fly them to Earth.

Two asteroid sample return missions are also in progress, the NASA’s OSIRIS-REx mission to Bennu and the Japan Aerospace Exploration Agency (JAXA’s)  Hayabusa2 mission to the Ryugu.  Both spacecraft are at or have already left their intended targets now and are expected to return with rock samples later this decade, with Hayabusa2 scheduled to complete its round trip later this year.

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

So sample return is in our future.  And in the case of Mars the samples will not with 100 percent certainty be lifeless — a major difference from the samples brought back from the moon during the Apollo missions and the samples coming from asteroids.

This possibility of a spacecraft bringing back something biological — as in the 1969 book “The Andromeda Strain” — has always been viewed as a very low probability but high risk hazard, and much thinking has already gone into how to bring samples back safely.… Read more

Close and Tranquil Solar System Has Astronomers Excited

An artist’s impression of the GJ 887 planetary system of super Earths. (Mark Garlick)

From the perspective of planet hunters and planet characterizers,  a desirable solar system to explore is one that is close to ours, that has a planet (or planets) in the star’s habitable zone,  and has a host star that is relatively quiet.  This is especially important with the very common red dwarf stars,  which are far less luminous than stars such as our sun but tend to send out many more powerful — and potentially planet sterilizing — solar flares.

The prolific members of the mostly European and Chilean Red Dots astronomy team believe they have found such a system about 11 light years away from us.  The system — GJ 887 — has an unusually quiet red dwarf host, has two planets for sure and another likely that orbits at a life-friendly 50-day orbit.  It is the 12th closest planetary system to our sun.

It is that potential third planet, which has shown up in some observations but not others, that would be of great interest.  Because it is so (relatively) close to Earth, it would be a planet where the chemical and thermal make-up of its atmosphere would likely be possible to measure.

The Red Dots team — which was responsible for the first detection of a planet orbiting Proxima Centauri and also Barnard’s star — describes the system in an article in the journal Science.  Team leader Sandra Jeffers of Goettingen University in Germany said in an email that GJ 887  “will be an ideal target because it is such a quiet star — no starspots or energetic outbursts  or flares.”

In an accompanying Perspective article in Science,  Melvyn Davies of Lund University in Sweden wrote that “If further observations confirm the presence of the third planet in the habitable zone, then GJ 887 could become one of the most studied planetary systems in the solar neighborhood.”

An artist’s impression of a flaring red dwarf star and a nearby planet. Red dwarfs are by far the most common stars in the sky, and most have planetary systems.  But scientists are unsure if they can support a habitable planet because many send out more large and powerful flares than other types of stars, especially at the beginnings of their solar lives. (Roberto Molar Candanosa/Carnegie/NASA)

GJ 877 is roughly half as massive as our sun — large for its type of star — and is the brightest red dwarf in the sky.… Read more

For First Time, Tiny CubeSat Locates a Distant Exoplanet

 

The image above, courtesy of NASA’s Jet Propulsion Laboratory, shows the CubeSat ASTERIA as it was being launched from the International Space Station in 2017.

The size of a briefcase, ASTERIA is part of a growing armada of tiny spacecraft being launched around the world and adding an increasingly important (and inexpensive) set of new tools for conducting Earth, space and exoplanet science.

ASTERIA, for instance, was designed to perform some of the complex tasks much larger space observatories use to study distant exoplanets outside our solar system.   And a new paper soon to be published in the Astronomical Journal describes how ASTERIA (short for Arcsecond Space Telescope Enabling Research in Astrophysics) didn’t just demonstrate it could perform those tasks but went above and beyond, detecting the known exoplanet 55 Cancri e.

While it was not the first detection of that exoplanet — which orbits close to its host star 41 light years away — it was the first time that a CubeSat had measured the presence of an exoplanet, something done so far only by much more sophisticated space and ground telescopes.

“Detecting this exoplanet is exciting because it shows how these new technologies come together in a real application,” said Vanessa Bailey, who led the ASTERIA  exoplanet science team at JPL.  The project was a collaboration between JPL and the Massachusetts Institute of Technology.

“We went after a hard target with a small telescope that was not even optimized to make science detections – and we got it, even if just barely,” said Mary Knapp, the ASTERIA project scientist at MIT’s Haystack Observatory and lead author of the study. “I think this paper validates the concept that motivated the ASTERIA mission: that small spacecraft can contribute something to astrophysics and astronomy.”  Both made their comments in a JPL release.

 

Artist rendering of planet Cancri 55 e. (NASA; JPL/Caltech)

 

ASTERIA was originally designed to spend 90 days in space.  But it received three mission extensions before the team lost contact with the satellite in late 2019.

The mission was not even designed to look for exoplanets.  It was, rather, a technology demonstration, with the mission’s goal to develop new capabilities for future missions. The team’s technological leap was to build a small spacecraft that could conduct fine pointing control — essentially the ability to stay focused very steadily on a distant star for long periods.… Read more

The WFIRST Space Observatory Becomes the Nancy Grace Roman Space Telescope. But Will it Ever Fly?

An artist’s rendering of NASA’s Wide Field Infrared Survey Telescope (WFIRST), now  the Nancy Grace Roman Space Telescope, which will search for exoplanets that are small rocky as well as Neptune sized at a greater distance from their host stars than currently possible.  It will also study multiple cosmic phenomena, including dark energy and other theorized Einsteinian phenomena. (NASA’s Goddard Space Flight Center)

Earlier last week, NASA put out a release alerting journalists to  “an exciting announcement about the agency’s Wide Field Infrared Survey Telescope (WFIRST) mission.”

Given the controversial history of the project — the current administration has formally proposed cancelling it for several years and the astronomy community (and Congress) have been keep it going — it seemed to be a  newsworthy event, maybe a breakthrough regarding an on-again, off-again very high profile project.

And since WFIRST was the top large mission priority of the National Academies of Sciences some years ago — guidance that NASA almost always follows — the story could reflect some change in the administration’s approach to the value of long-established scientific norms.  Plus, it could mean that a space observatory with cutting-edge technology for identifying and studying exoplanets and for learning much more about dark matter and Einsteinian astrophysics might actually be launched in the 2020s.

But instead of a newsy announcement about fate of the space telescope, what NASA disclosed was that the project had been given a new name — the Nancy Grace Roman space telescope.

As one of NASA’S earliest hired and highest-ranking women, Roman spent 21 years at NASA developing and launching space-based observatories that studied the sun, deep space, and Earth’s atmosphere. She most famously worked to develop the concepts behind the Hubble Space Telescope, which just spent its 30th year in orbit.

This is a welcome and no doubt deserving honor.  But it will be much less of an honor if the space telescope is never launched into orbit.  And insights into the fate of WFIRST (the Nancy Grace Roman Space Telescope) are what really would constitute “an exciting announcement.”

What’s going on?

Nancy Grace Roman at NASA’s Goddard Space Flight Centre in the early 1970s (NASA)

 

I have no special insights, but I think that one of the scientists on the NASA Science Live event was probably on to something when she said:

“I find it tremendously exciting that the observatory is being  renamed,”  said Julie McEnery, deputy project scientist for the (now) NASA Roman mission.  … Read more

Mapping the Surfaces of Our Solar System

 

A portion of the new “unified” geological map of the moon. (NASA/GSFC/USGS.)

It was not all that long ago that a “map” of our  moon, of Mars, of a large asteroid such as Vesta, of Titan, or of any hard-surfaced object in our solar system would have some very general outlines, some very large features identified,  and  then the extraterrestrial equivalent of the warning on Earth maps of yore that beyond a certain point “there be dragons.”  Constructing a map of the topography and geology of a distant surface requires deep understanding and data and lot of hard work.

Yet such an in-depth mapping is underway and has already resulted in detailed surface rendering of Mars,  of Jupiter’s moons Ganymede and Io, and of our moon.  And now, using both Apollo-era data for the moon and measurements from the Japanese lunar orbiter and currently flying American orbiter, the U.S. Geological Survey, in partnership with NASA and the Lunar and Planetary Institute,  has produced a rendering of our moon that moves extraterrestrial mapping significantly further.

It unifies all the data collected using a variety of techniques and produces a map with well-defined geological units, with in-laid topography (on digital versions,) and with a guide of sorts for moon watchers on Earth.  The red sections in the map above are the basalt lava flows that have the fewest craters from asteroid hits and so are the youngest surfaces.  They are also the darker sections of the moon that we see when we look into the night sky at a full moon.

The maps are not at a detail to allow NASA mission planners to assess a landing site, but they do tell what the geological environs are going to be and so are a guide to what might be found.

 

Orthographic projections (presenting three-dimensional objects in two-dimensions)  of the new “Unified Geologic Map of the Moon” showing the geology of the moon’s near side (left) and far side (right) with shaded topography from the Lunar Orbiter Laser Altimeter (LOLA). This geologic map is a synthesis of six Apollo-era regional geologic maps, updated based on data from recent satellite missions. It will serve as a reference for lunar science and future human missions to the Moon.  (NASA/GSFC/USGS.)

The chief purpose of the map — in which 5 kilometers of distance are represented by 1 millimeter on the map — is to summarize the current state of lunar geologic knowledge.… 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

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