Many Worlds

Category: Planetary and Solar System Characteristics (page 1 of 6)

Pam Conrad: The NASA Astrobiologist Who Also Became a Minister

April 13, 2023 / / 0 Comments

Pan Conrad on her last Sunday as rector of St. Albans Episcopal Church in Glen Burnie, Maryland. (Julian Lahdelma)

Science and religion so often seem to be in conflict, with the chasm between them widening all the time.

For many, the grounding of their religion is in faith and belief in powers beyond our understanding.  For people of science, the grounding is in empirical facts and measurements that can be tested to help explain our world.

The conflicts between science and religion have been many,  perhaps most intensely on issues including evolution, how life on Earth began and how our universe came to be.

The era of pioneering scientists being punished or hounded by religious leaders — think of Galileo, astrobiologist-before-his-time Giordano Bruno, Charles Darwin — is largely in the past.  But so too is the era when the most prominent natural scientists were profoundly religious people, such as Sir Isaac Newton, James Maxwell (who correctly theorized the nature of electromagnetism) and one of the 19th century physicist and scientific titan, Lord Kelvin.

The field of astrobiology presents innumerable issues where a scientific and religious focus certainly could clash.  Astrobiology is focused on the search for life beyond Earth which, if detected, could raise significant issues for some religious people.

The astrobiology effort is grounded in our scientific theories of how the universe began and evolved over its 13.6 billion years, so spiritual and religious views that once dominated thinking about these questions play little role.

And then there is the origin-of-life issue, which is also part of astrobiology and is, of course, an arena where scientific and religious views are often in conflict.

With so many divides between a scientific and a religious approach to astrobiological questions, it might seem that there is little room for overlap.

Conrad has worked on the characterization of biosignatures and the habitability of Mars, first at JPL and now at the Earth and Planets Laboratory at the Carnegie Institution of Science. She worked on the science team of the Curiosity rover on Mars and now she works with three instruments on the Perseverance rover at Jezero Crater, Mars. (NASA)

But then I spoke with the Rev. Pamela Conrad, who I knew from some years ago when we often talked about astrobiology and even took a trip to Death Valley together, where she helped me understand some of the science of life surviving in extreme environments and how to find it.… Read more

What the JWST is Learning About Exoplanet Atmospheres

April 5, 2023 / / 0 Comments

We are now well into the era of exoplanet atmospheres, of measurements made possible by the James Webb Space Telescope.  While prior observatories could detect some chemicals in exoplanet atmospheres,  the limits were substantial. This is an artist’s impression of a hot Jupiter with a thick atmosphere transiting its host star. (NASA, ESA, and G. Bacon (STScI)

The James Webb Space Telescope is beginning to reveal previously unknowable facts about the composition of exoplanets — about the presence or absence of atmospheres around the exoplanets and the makeup of any atmospheres that are detected.

The results have been coming in for some months and they are a delight to scientists.  And as with most things about exoplanets, the results are not always what were expected.

For instance, gas giant planets  orbiting our Sun show a clear pattern; the more massive the planet, the lower the percentage of “heavy” elements (anything other than hydrogen and helium) in the planet’s atmosphere.

The James Webb Space Telescope is returning insights into the atmospheres of exoplanets that scientists have long dreamed about obtaining. Some are predicting a new era in exoplanet research. (NASA)

But out in the galaxy, the atmospheric compositions of giant planets do not fit the solar system trend, an international team of astronomers has found.

Researchers discovered that the atmosphere of exoplanet HD149026b, a “hot jupiter” given the name “Smertrios” that orbits a Sun-like star, is super-abundant in the heavier elements carbon and oxygen – far above what scientists would expect for a planet of its mass.

In its “early release” program for exoplanet results, JWST also observed WASP-39 b, a “hot Saturn” (a planet about as massive as Saturn but in an orbit tighter than Mercury) orbiting a star some 700 light-years away.

The atmosphere around the planet provided the first detection in an exoplanet atmosphere of sulfur dioxide (SO2), a molecule produced from chemical reactions triggered by high-energy light from the planet’s parent star.

The Trappist-1 system –seven Earth-sized planets orbiting a red dwarf star only 40 light-years away — is another subject of great interest and JWST has provided some exciting results there too.

While the first Trappist-1 planet studied — the one nearest to the star — apparently has no atmosphere, JWST was able to in effect take the planet’s temperature.  The telescope captured thermal signatures from the planet, which is another first.

When starlight passes through a planet’s atmosphere, certain parts of the light are absorbed by the atmosphere’s elements.

… Read more

A Scientific Bonanza From Asteroid Ryugu and Hayabusa2

February 23, 2023 / / 1 Comment

Optical microscope images of six particle samples that were selected from what Hayabusa2 brought back to Earth from asteroid Ryugu. {Japan Aerospace Expedition Agency (JAXA), Science.}

Collecting and transporting back to Earth samples of other planets, moons, asteroids and comets is extremely difficult, costly and time-consuming.  But as just-released papers based on Japan’s Hayabusa2 sample return mission to the asteroid Ryugu make abundantly clear, the results can be fabulous.

In a series of articles in the journal Science, scientists who studied the samples (which were returned to Earth in late 2020) and commentators marvel at the opportunity to study material that was formed as the solar system itself formed — more than 4.5 billion years ago.

The sample contains thousands of different organic (carbon-based) molecules of different kinds, including amino acids and a range of aromatic hydrocarbons.  There are also many minerals formed in the presence of water.

This composition was not a big surprise based on other similar carbon-based meteorites that have fallen to Earth. But they were totally clean samples that were in no way contaminated by life and  physical conditions on our planet. They also had not made the fiery passage through our atmosphere before landing and becoming a meteorite that someone may chance to find.

What they are, then, are pristine examples of the early solar system — solar system baby pictures — with the chemistry and physical thumbprints of the solar nebula and interstellar space from which our Sun and solar system were formed.

The asteroid Ryugu at 30 miles, as photographed by Hayabusa2.  Ryugu is a near-Earth asteroid, far from the main asteroid belt between Mars and Jupiter.   (JAXA, University of Tokyo and collaborators)

The return capsule brought back about 10 grams of the asteroid.  That might not seem like a lot, but it was more than enough to learn a great deal about an important asteroid from an ancient asteroid family.

As Hiroshi Naraoka of Kyushu University and his colleagues conclude in their Ryugu paper, “Meteorites made of material similar to Ryugu may have delivered amino acids and other prebiotic organic molecules to the early Earth and other rocky planets — providing the building blocks of life.”

Ryugu provides the best chance to date to study what precisely could have been delivered.

Hayabusa2 touchdown on asteroid Ryugu in 2019. (JAXA)

The studies together tell the history of Ryugu, its history and its composition. … Read more

A New Twist On Planet Formation

January 30, 2023 / / 1 Comment

This image of the nearby young star TW Hydrae reveals the classic rings and gaps that signify planets are being formed in this protoplanetary disk. {ESO, Atacama Large Millimeter/submillimeter Array (ALMA)}

Before the first exoplanets were discovered in the 1990s,  our own solar system served as the model for what solar systems looked like.  The physical and chemical dynamics that formed our system were also seen as the default model for what might have occurred in solar systems yet to be found.

As the number of exoplanets identified ballooned via the Kepler Space Telescope and others, and  it became clear that exoplanets were everywhere and orbiting most every star, the model of our own solar system became obviously flawed.  The first exoplanet identified, after all, was a “hot Jupiter” orbiting very close to its star — a planetary placement previously thought to be impossible.

With the growing number of known exoplanets and their most unusual placements, the field of planet formation — focused earlier on understanding on how the planets of our system came into being and what they were made of — expanded to take in the completely re-arranged planetary and solar system menagerie being found.

This was basic science seeking to understand these newfound worlds, but it also became part of the fast-growing field of astrobiology, the search for planets that might be habitable like our own.

In this context, planet formation became associated with the effort to learn more about the dynamics that actually make a planet habitable — the needed composition of a planet, the nature of its Sun, its placement in a solar system and how exactly it was formed.

So the logic of planet formation became the subject of myriad efforts to understand what might happen when a star is born, surrounded by a ring of gas and dust that will in time include larger and larger collections of solids that can evolve into meteors, planetesimals and if all goes a particular way, into planets.

A thin section of primitive meteorite under a microscope. The various colors suggest different minerals that comprise meteorites. The round-shaped mineral aggregates are called chondrules, which are among the oldest known materials in our solar system. (Science)

As part of this very broad effort to understand better how planets form, meteorites have been widely used to learn about what the early solar system was like. Meteorites are from asteroids that formed within the first several million years of planetary accretion.… Read more

The World of Water Worlds

December 22, 2022 / / 1 Comment

Artist rendering of a water world exoplanet. NASA predicts that quite a few exist in the galaxies but none has been confirmed. Two new candidates have been put forward. (The Cosmic Companion)

Among the most intriguing types of exoplanet expected to be orbiting distant stars is the  “water world,” planets that are liquid to a far, far greater extent than on Earth.

Astronomers have theorized the existence of such planets and several candidates have been put forward, though not confirmed.  But the logic is strong enough for NASA scientists to conclude there are likely many of them in our galaxy.

Now two new potential water worlds have been proposed in a planetary system 218 light years away.

Using both the Hubble Space Telescope and data from the retired Spitzer Space Telescope, a team from Montreal has identified  the planets circling a red dwarf star.  Water, they propose, may well make up a significant portion of the planets.

Though the telescopes can’t directly observe the planets’ surfaces, other paths to identifying a water world are known.  By determining the planets’ densities through measurements of their weight and radii (and then volume), these planets — which would normally be described as “super-Earths because of their size — are lighter than rock worlds but heavier than gas-dominated ones.

… Read more

New Research Finds The Very Early Solar System Went Through an Especially Intense Period of Asteroid Collisions

June 14, 2022 / / 0 Comments

An artist’s view of the very early solar system, where dust was collecting into small rocks, which smashed into each other and some became larger. The height of the crash-ups took place during a surprisingly short period of time. (Tobias Stierli, flaeck / PlanetS)

In the earliest days of our solar system — before any planets had been cobbled together — the recently formed Sun was circled by cosmic gas and dust. Over time, fragments of rock formed from the dust and many of these orbiting rocks smashed together and some became the gradually larger components of planets-to-be.  Others were not part of any planet formation and became asteroids orbiting the Sun, and sometimes falling to Earth as meteorites.

Scientists have found that these asteroids (and their Earth-bound pieces) remained relatively unchanged since their formation billions of years ago.

And so they provide an archive of sorts, in which the conditions of the early solar system are preserved.

Alison Hunt, a planetary scientist at ETH Zurich in Switzerland, led a team that looked at some of that early solar system history and came up with some surprising results.

She and her team at the Swiss National Centre of Competence in Research (NCCR) PlanetS found that almost all of the asteroidal-cores-turned-meteorites they studied had been formed in a short four-million-year period starting almost eight million years the solar system first came into being.  A four million-year time span is short in astronomical terms and also unusual in terms of the precision achieved for the dating.

These results, and some inferences about why this period was so chaotic in the early solar system, were reported in Nature Astronomy late last month.

But before we look at why this might have happened, let’s explore a bit about how the team achieved such precise data about when many asteroids were formed.

One of the iron meteorite samples the team analyzed that was, long ago, the core of an asteroid. (Aurelia Meister)

To access this asteroid/meteorite archive, the researchers had to prepare and examine the extraterrestrial material from iron meteorites that had fallen to Earth.  Once part of the metallic cores of asteroids, samples from 18 different iron meteorites were used in the analysis.

The researchers first had to dissolve the samples to be able to isolate the elements palladium, silver and platinum — the key to their efforts.

Using a mass spectrometer they measured abundances of different and identifiable isotopes of these elements, and with their results they could put tighter constraints on the timing of events in the early solar system.

… Read more

The World’s Most Capable Space Telescope Readies To Observe. What Will Exoplanet Scientists Be Looking For?

March 28, 2022 / / 0 Comments

This artist’s concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets’ diameters, masses and distances from the host star.  The James Webb is expected to begin science observations this summer. (NASA/JPL-Caltech)

The decades-long process of developing, refining, testing, launching, unfurling and now aligning and calibrating the most capable space telescope in history is nearing fruition.  While NASA has already released a number of “first light” images of photons of light moving through the James Webb Space Telescope’s optical system, the  jaw-dropping “first light” that has all the mirrors up and running together to produce an actual scientific observation is a few months off.

Just as the building and evolution of the Webb has been going on for years, so has the planning and preparation for specific team observation “campaigns.”   Many of these pertain to the earliest days of the universe, of star and galaxy formation and other realms of cosmology,  but an unprecedented subset of exoplanet observations is also on its way.

Many Worlds earlier discussed the JWST Early Release Science Program, which involves observations of gigantic hot Jupiter planets to both learn about their atmospheres and as a way to collect data that will guide exoplanet scientists in using JWST instruments in the years ahead.

Now we’ll look at a number of specific JWST General Observation and Guarantreed Time efforts that are more specific and will collect brand new information about some of the major characteristics and mysteries of a representative subset of the at least 100 billion exoplanets in our galaxy.

This will be done by using three techniques including transmission spectroscopy — collecting and analyzing the light that passes through an exoplanet’s atmosphere as it passes in front of its Sun.  The JWST will bring unprecedented power to characterizing the wild diversity of exoplanets now known to exist; to the question of whether “cool” and dim red dwarf stars (by far the most common in the galaxy) can maintain atmospheres; to newly sensitive studies of the chemical makeup of exoplanet atmospheres; and to the many possibilities of the TRAPPIST-1 exoplanets, a seven rocky planet solar system that is relatively nearby.

An artist’s interpretation of GJ 1214b,one of a group of super-Earth to mini-Neptune sized planets to be studied in the JWST Cycle1 observations. The planet is known to be covered by a thick haze which scientists expect the JWST to pierce as never before and allow them to study atmospheric chemicals below.

… Read more

What The James Webb Space Telescope Can Do For Exoplanet Science and What It Cannot Do

December 17, 2021 / / 3 Comments

The James Webb Space Telescope, as rendered by an artist. The telescope is scheduled to launch later this month. (NASA)

When the James Webb Space Telescope finally launches (late this month, if the schedule holds) it will forever change astronomy.

Assuming that its complex, month-long deployment in space works as planned, it will become the most powerful and far-seeing observatory in the sky.  It will have unprecedented capabilities to probe the earliest days of the universe, shedding new light on the formation of the first stars and galaxies.  And it will observe in new detail the most distant regions of our solar system.

Deep space astrophysics is what JWST was first designed for in the early 1990s, and that will be its transformative strength.

But much is also being made of what JWST can do for the study of exoplanets and some are even talking about how it just might be able to find biosignatures — signs of distant life.

While it is probably wise to never say never regarding an observatory with the power and capabilities of JWST,  the reality is that it was not designed to look for the exoplanets most likely to be habitable.  Actually, when it was first proposed, the observatory had no exoplanet-studying capabilities at all because no exoplanets had yet been found.

What was added on is substantial and exoplanet scientists say JWST can help advance the field substantially.  But there are definite limits and finding biosignatures — life — is almost certainly a reach too far for JWST.

When starlight passes through a planet’s atmosphere, certain parts of the light are absorbed by the atmosphere’s elements. By studying which parts of light are absorbed, scientists can determine the composition of the planet’s atmosphere. (Christine Daniloff/MIT, Julien de Wit)

Astronomer Jacob Bean of the University of Chicago, who has played a leadership role in planning JWST exoplanet observations for the telescope’s early day, says that people need to know these limitations so the pioneering exoplanet science that will be possible with JWST is not seen as somehow disappointing.

As he explained, it is essential to understand that the kind of exoplanet observing that the JWST will mostly do is “transit spectroscopy.”  This involves staring at a star when an exoplanet is expected to transit in front of it.  When that happens, light from the star will pass through the atmosphere of the exoplanet (if there is one) and through spectroscopy scientists can determine what molecules are in that hoped-for atmosphere.… Read more

Why Does Our Solar System Have No Super-Earths, and Other Questions for Comparative Planetology

December 1, 2021 / / 0 Comments

An artist’s impression of the exoplanet LHS 1140b, which orbits a red dwarf star 40 light-years from Earth. Using the European Southern Observatory’s telescope at La Silla, Chile, and other telescopes around the world, an international team of astronomers discovered this super-Earth orbiting in the habitable zone around the faint star LHS 1140. This world is a little larger and much more massive than the Earth. (ESO)

Before the explosion in discovery of extrasolar planets, the field of comparative planetology was pretty limited  — confined to examining the differences between planets in our solar system and how they may have come to pass.

But over the past quarter century, comparative planetology and the demographics of planets came to mean something quite different.  With so many planets now identified in so many solar systems, the comparisons became not just between one planet and another but also between one solar system and another.

And the big questions for scientists became the likes of:  How and why are the planetary makeups of distant solar systems often so different from our own and from each other; what does the presence  or absence of large planets in a solar system do to the distribution of smaller planets;  how large can a rocky planet can get before it turns to a gas giant planet; and on a more specific subject, why do some solar systems have hot Jupiters close to the host star and others have cold Jupiters much further out like our own

Another especially compelling question involves our own solar system, though as something of an outlier rather than a prototype.

That question involves the absence in our solar system of anything in the category of a “super-Earth” — a rocky or gaseous extrasolar planet with a mass greater than Earth’s but substantially below those of our solar system’s planets next in mass,  Uranus and Neptune.

The term “super-Earth” refers only to the mass and radii of the planet, and so does not imply anything about the surface conditions or habitability. But in the world of comparative planetology “super-Earths” are very important because they are among the most common sized exoplanets found so far and some do seem to have planetary characteristics associated with habitability.

Yet they do not exist in our solar system.  Why is that?

Artist rendition of Earth in comparison to one of the many super-Earth planets. (NASA)

In a recent article in The Astrophysical Journal Letters,  planetary demographer Gijs D.… Read more

Many Planets Form in a Soup of Life-Friendly Organic Compounds

October 14, 2021 / / 0 Comments

Artist’s depiction of a protoplanetary disk with young planets forming around a star. The right-side panel zooms in to show various organic molecules that are accreting onto a planet. (M.Weiss/Center for Astrophysics | Harvard & Smithsonian)

One of the more persuasive arguments in favor of the potential existence of life beyond Earth is that the well-known chemical building blocks of that life are found throughout the galaxy.  These chemical components aren’t all present in all examined solar systems and planets, but they are common and behave in ways familiar to scientists here.

And when it comes elements and compounds found on distant planets but not found here, there just aren’t many. That doesn’t mean they don’t exist — some unstable compounds in interstellar space, for instance — but rather that the cosmos holds many surprises but none have involved extraterrestrial elements or compounds near planets or stars.

This is in large part the result of how elements are formed in the universe.  Other than hydrogen and helium, all other elements are forged in the thermonuclear explosion of stars that have exhausted their supply of fuel.  These massive explosions (supernovae) then shoot the newly-formed elements out into space where they can and do collect in gas and dust clouds that will form other new stars.  They are spread throughout the disks that form around new stars and over time they become components of new planets in formation.

This galactic evolution includes the bonding together of carbon-based organic compounds — the building blocks of life as we know it.  They are an essential component to any theory of a planet’s habitability and,  while their presence in space and star nurseries has been known for some time,  they have remained a subject of great interest but limited detailed knowledge.

That is why an international team from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. set out to intensively study five disks forming around young stars to determine more precisely what organic compounds were present and available for objects developing into planets.

And the results are striking:  The abundance of organic material detected was 10 to 100 times more than expected.

“These planet-forming disks are teeming with organic molecules, some of which are implicated in the origins of life here on Earth,” said team leader Karin Öberg. “This is really exciting; the chemicals in each disk will ultimately affect the type of planets that form and determine whether or not the planets can host life.”… Read more

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