Many Worlds

Category: Planetary Systems (page 1 of 15)

Destination: Europa

May 8, 2023 / / 0 Comments

An artist rendering of Europa Clipper over Europa. The spacecraft is scheduled to launch in fall 2024.  (NASA/JPL)

“ALL THESE WORLDS ARE YOURS – EXCEPT EUROPA. ATTEMPT NO LANDING THERE.”

These are the words broadcast by the computer HAL as recounted in Arthur C. Clarke’s book “2010: Odyssey Two,” the sequel to the iconic “2001: A Space Odyssey.”

The message had been delivered to the computer by the non-corporeal David Bowman (the focus of the “2001”), but more accurately from the energy-based aliens who control the fate of Bowman, the famous monoliths and much more.  The aliens had concluded that Europa, with its subsurface ocean, could support life with the potential to evolve, and so they wanted the Jovian moon to be protected from meddling by humans or anyone else.

Clarke’s “Odyssey Two” was released in 1982, when Europa was not exactly a front-burner destination for NASA or anyone else.

But much has changed, and Clarke’s early focus on Europa as the most potentially habitable object in the solar system has been embraced by NASA and others for some time.

Surface features of Jupiter’s icy moon Europa are revealed in an image obtained by Juno’s Stellar Reference Unit (SRU) during the spacecraft’s flyby in 2022.  The spacecraft came within 219 miles of the moon.
(NASA/JPL-Caltech/SwRI)

While the fictional admonition not to land on Europa is (for now, a least) being respected,  the pull of Europa has become enormously strong.

Consider:

The NASA spaceship Juno recently performed a flyby of the moon and took some revealing new photos. (See above.)

Just last month, the European Space Agency launched the Jupiter Icy Moons Explorer (JUICE)  spacecraft that is headed to Jupiter and three Jovian moons, including Europa.

And now all the parts and instruments of NASA’s Europa Clipper are in a Jet Propulsion Lab clean room for assembly in preparation for an October, 2024 launch. The Clipper will not land on Europa, but it will get closer than any other spacecraft has come.

So while it won’t be until the early 2030s that JUICE and the Clipper have their close encounters with Europa, the moon is very much on the front burner now for astrobiologists, planetary scientists and space (and science fiction) aficionados of all kinds.

This composite includes the four largest moons of Jupiter which are known as the Galilean satellites. These moons were first identified by the Italian astronomer Galileo Galilei in 1610.

… Read more

Pam Conrad: The NASA Astrobiologist Who Also Became a Minister

April 13, 2023 / / 1 Comment

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

What Would Happen If Our Solar System Had a Super-Earth Like Many Others? Chaos.

March 13, 2023 / / 1 Comment

Our solar system’s rocky planets are tiny compared with the larger gas and ice giants. Exoplanet research has found, however, that the most common planets in the galaxy appear to be super-Earths and sub-Neptunes, types of planets not found in our system. Size comparison of the planets. (Alexaldo/iStock/Getty)

Before astronomers began to find planets — many, many planets — orbiting Suns other than ours,  the scientific consensus was that if other solar systems were ever found they would probably look much like ours.  That would mean small, rocky planets closest to the Sun and large gaseous planets further out.

That assumption crash and burned with the discovery of the first discovery of an exoplanet orbiting a star — 51 Peg.  It was a hot, Jupiter-sized planet that circled its Sun in four days.

That planetary rude awakening was followed by many others, including the discovery of many rocky planets much larger than those in our system which came to be called  super-Earths.  And equally common are gaseous planets quite a bit smaller than any near us, given the name sub-Neptunes.

Many papers have been written theorizing why there are no super-Earth or sub-Neptunes in our solar system.  And now astrophysicist Stephen Kane of the University of California, Riverside has taken the debate another direction by asking this question:  What would happen to our solar system planets if a super-Earth or sub-Neptune was present?

The results of his dynamic computer simulations are not pretty: the orbits of many of our planets would change substantially and that would ultimately result in some being kicked out of the solar system forever.  The forces of orbit-transforming gravity set loose by the addition of a super-Earth are strong indeed.

The term super-Earth is a reference only to an exoplanet’s size – larger than Earth and smaller than Neptune – but not suggesting they are necessarily similar to our home planet. The true nature of these planets, such as Gliese 832c, above, remains ambiguous because we have nothing like it in our own solar system. Super-Earths they are common among planets found so far in our galaxy. (Planetary Habitability Laboratory/University of Puerto Rico at Arecibo)

Let’s go back to our actual solar system for some context.

The gap in size between the size of our terrestrial planets and giant gas planets is great. The largest terrestrial planet is Earth, and the smallest gas giant is Neptune, which is four times wider and 17 times more massive than Earth.… Read more

A Scientific Bonanza From Asteroid Ryugu and Hayabusa2

February 23, 2023 / / 2 Comments

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 JWST Discovers its First Earth-Sized Exoplanet

January 17, 2023 / / 0 Comments

Artist rendering of LHS 475 b, an Earth-sized exoplanet recently identified using the James Webb Space Telescope. This was the first planet of its size detected by the JWST. {NASA / ESA / CSA / Leah Hustak (STScI)}

In the search for life on distant planets, scientists generally focus on identifying Earth-sized, rocky planets, finding planets in their host star’s habitable zone, and having available the telescope power to read the chemical make-up of the atmospheres.

A relatively small number of Earth-sized exoplanets discovered by telescopes in space and on Earth have meet some of the key characteristics.  But now with the James Webb Space Telescope in operation, with its 21-foot high-precision mirror, scientists have been looking forward to finding small, rocky planets that meet all the key criteria.

And during its first year of operation, the JWST  has already found and studied one small planet that meets at least some or those criteria.  The planet identified, called LHS 475 b, is nearly the same size as Earth, having 99% of our planet’s diameter, scientists said, and is a relatively nearby 41-light-years away.

The research team that detected the small planet is led by Kevin Stevenson and Jacob Lustig-Yaeger, both of the Johns Hopkins University Applied Physics Laboratory.

The team chose to observe this target with Webb after reviewing targets of interest from NASA’s Transiting Exoplanet Survey Satellite (TESS), which hinted at the planet’s existence. Webb’s Near-Infrared Spectrograph (NIRSpec) captured the planet easily and clearly with only two transit observations.

“There is no question that the planet is there,” said Lustig-Yaeger. “Webb’s pristine data validate it.”

“With this telescope, rocky exoplanets are the new frontier.”

The TRAPPIST-1 system contains a total of seven known Earth-sized planets orbiting a weak red dwarf star. Three of the planets — TRAPPIST-1e, f and g — are located in the habitable zone of the star (shown in green in this artist’s impression), where temperatures are potentially moderate enough for liquid water to exist on the surface.  As a comparison to the TRAPPIST-1 system the inner part of the Solar System and its habitable zone is shown. (NASA)

Earth-sized exoplanets have been found earlier.  The Trappist-1 system, only 39 light-years away, is famously known to include seven small, rocky planets, and it was detected by a small, ground-based telescope.

The Kepler Space Telescope also detected a debated but significant number of Earth-sized planets during its nine-year survey of one small section of the distant sky last decade. … 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

The Cosmos, As Viewed By The James Webb Space Telescope

November 7, 2022 / / 0 Comments

The iconic “Pillars of Creation” image, on left, was taken in visible light by the Hubble Space Telescope in 2014. A new, near-infrared-light view from NASA’s James Webb Space Telescope, at right, helps us peer through more of the dust in this star-forming region. The thick, dusty brown pillars are no longer as opaque and many more red stars that are still forming come into view.  The pillars of gas and dust seem darker and less penetrable in Hubble’s view, and they appear more permeable in Webb’s. (NASA)

The James Webb Space Telescope was developed to allow us to see the cosmos in a new way — with much greater precision, using infrared wavelengths to piece through dust around galaxies, stars and planets, and to look further back into time and space.

In the less than four months since the first Webb images were released,  the pioneering telescope has certainly shown us a remarkable range of abilities.  And as a result, we’ve been treated to some dazzling new views of the solar system, the galaxy and beyond.  This is just the beginning and we thankfully have years to come of new images and the scientific insights that come with them.

Just as the Hubble Space Telescope, with its 32 years of service and counting, ushered in a new era of space imagining and understanding, so too is the Webb telescope revolutionizing how we see and understand our world writ large.  Very large.

Neptune as seen by Voyager 2 during a flyby more than three decades ago, the Hubble Space Telescope last year, and the JWST this summer. ( NASA/ESA/CSA))

The differences between the Webb’s image and previous images of Neptune are certainly dramatic, in terms of color, precision and what they tell us about the planet.

Surely most striking in Webb’s new image is the crisp view of the planet’s rings, some of which have not been seen since NASA’s Voyager 2 became the first spacecraft to observe Neptune during its flyby in 1989. In addition to several bright, narrow rings, the Webb image clearly shows Neptune’s fainter, never-seen dust bands as well.

Neptune is an ice giant planet. Unlike Jupiter and Saturn, which consist primarily of hydrogen and helium, Neptune has an interior that is much richer in heavier elements (“heavier is the sense of not hydrogen or helium.) One of the most abundant heavy molecules is methane, which appears blue in Hubble’s visible wavelengths but largely white in the Webb’s near-infrared camera.… Read more

The Juno Spacecraft Images Jupiter’s Moon Europa as it Speeds Past

September 30, 2022 / / 0 Comments

The first image from NASA’s Juno spacecraft as it passed close by Europa as part of its extended mission.  (NASA)

For NASA to extend its space science missions well past their original lifetime in space has become such a commonplace that it is barely noticed.

The Curiosity rover was scheduled to last on Mars for two years but now it has been going for a decade — following the pace set by earlier, smaller Mars rovers.  The Cassini mission to Saturn was extended seven years beyond it’s original end date and nobody expected that Voyager 1, launched in 1977,  would still flying out into deep space and sending back data 45 years later.

The newest addition to this virtuous collection of over-achievers is the Juno spacecraft, which arrived at Jupiter in 2016.  Its prime mission in and around Jupiter ended last year and then was extended until 2025, or beyond.

And now we have some new and intriguing images of Jupiter’s moon Europa thanks to Juno and its extension.

Traveling at a brisk 14.7 miles per second, Juno passed within 219 miles of the surface of the icy moon on Thursday and images from the flyby were released today (Friday.)  That gave the spacecraft only a two-hour window to collect data and images, but scientists are excited.

“It’s very early in the process, but by all indications Juno’s flyby of Europa was a great success,” said Scott Bolton, Juno principal investigator from Southwest Research Institute in San Antonio, in a NASA release.

“This first picture is just a glimpse of the remarkable new science to come from Juno’s entire suite of instruments and sensors that acquired data as we skimmed over the moon’s icy crust.”

Candy Hansen, a Juno co-investigator who leads planning for the Juno camera at the Planetary Science Institute in Tucson, called the released images “stunning.”

“The science team will be comparing the full set of images obtained by Juno with images from previous missions, looking to see if Europa’s surface features have changed over the past two decades,” she said.

An image of Europa taken by the Galileo spacecraft as it passed the moon in 1998. (NASA/JPL-Caltech)

During the flyby, the mission collected what will be some of the highest-resolution images of the moon (0.6 miles per pixel) taken so far and obtained valuable data on Europa’s ice shell structure, interior, surface composition, and ionosphere, in addition to the moon’s interaction with Jupiter’s magnetosphere.… Read more

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