Many Worlds

Category: Our Solar System (page 1 of 8)

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

The Strange Interstellar Object Oumuamua Was a Comet and Not The Space Probe Some Had Proposed

March 22, 2023 / / 0 Comments

New research concludes that the interstellar object that entered our solar system and then rocketed out was a small comet and not a spacecraft, as some had speculated. (JPL/NASA)

In 2017, an  unusual small object flew into our solar system from afar,  approached the inner solar system and the Sun and then sped back out to interstellar space.  In all, it was detected and followed for 11 days.

The object was puzzling because such interstellar visitors had not been observed before, and most mysterious because it accelerated in a most unusual way out of the solar system.  This was not the normal behavior of any object in the solar system.

The object, a few hundred meters in length, was first identified as an asteroid because it had not of the sparkle of a comet, and a “dark comet” was proposed, and  then  something perhaps sent by aliens to explore the solar system.  After all, the shape of the object known as ‘Oumuamua — Hawaiian for “Scout”– was described as reddish and sometimes shaped like a pancake and sometimes like a cigar.

‘Oumuamua became an object of great fascination among space scientists and even became the subject a popular book by a Harvard astronomer who argued that it was clearly an alien lightsail. That is, a probe that is propelled by the propulsive radiation of starlight itself.

Now, a paper offers a very different, and apparently quite compelling, explanation.,

In Nature, University of California, Berkeley astrochemist Jennifer Bregner and Cornell University astronomer Darryl propose that the comet’s mysterious deviations from a typical object’s path around the Sun can be explained by a simple physical mechanism likely common among many icy comets: outgassing of hydrogen as the comet warmed up in the sunlight.

What made ‘Oumuamua different from every other well-studied comet in our solar system was its size. It was so small that the gravitational nudge it received around the Sun was slightly altered by the tiny push created when hydrogen gas spurted out of the ice.

And that’s what caused the acceleration, the scientists say.

An artist rendering of ‘Oumuamua, the first known alien object to enter our solar system. It was identified by the Pan-STARRS 1 telescope in Hawaii. It was later followed by observatories around the world and astronomers generally concluded that it had been traveling for millions of years before its chance encounter with our solar system.

… 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

New Martian Surprise From The Curiosity Rover

February 13, 2023 / / 0 Comments

NASA researchers found that waves on the surface of a shallow lake in Gale Crater stirred up sediment billions of years ago. That sediment eventually creating rippled textures left in rock. (NASA/JPLVCaltech/MSSS)

In its more than a decade of exploring Gale Crater on Mars, the rover Curiosity has found innumerable signs of the presence of long-ago water.

There have been fossil streams, alluvial fans, lakes shallow and deep, deltas and countless examples of rocks infiltrated and chemically transformed in the presence of water.  The picture of the crater as a watery environment in the warmer and wetter days of Martian history — 4 billion to 3 billion years ago — is well established.

Nonetheless. it still came as a wonder that the rover came across the entirely unexpected remains of fossilized ripples in a shallow lake bed.  What was even more surprising is that it was found in an area previously determined to have little likelihood of having ever been wet.

“Billions of years ago, waves on the surface of a shallow lake stirred up sediment at the lake bottom, over time creating rippled textures left in rock,” NASA said in a statement last week.

It was the first time such a feature has been discovered in Gale Crater, although the rover has passed through numerous fossil lake beds.

The Marker Band is a continuous dark, thin and hard layer running from left to right (but thinning out on the left) setting off the region of the rippled rock bed.   Both its composition and origins are not well understood. (NASA/JPL-Caltech)

One of the mission’s main goals has been to find out if this area in the southern highlands of Mars might have once been habitable for microbial life.

It was determined within the first two years of the rover’s time in Gale Crater that the crater was indeed once habitable based on the past presence of significant amounts of water and chemicals left behind by that long-departed water. Understanding the crater’s history of water has been a central goal of the mission.

The Curiosity team was thrilled by their new find.

“This is the best evidence of water and waves that we’ve seen in the entire mission,” said Curiosity project scientist Ashwin Vasavada. “We climbed through thousands of feet of lake deposits and never saw evidence like this.”

The rippled fossils are in an area set off by a black, hard-rock line called the “Marker Band.”… Read more

Tantalizing Organic Compounds Found on Mars

November 29, 2022 / / 1 Comment

The NASA/ESA Perseverance rover on xxx. New findings tell of the presence of organic material — the building blocks of life — in several locations at Jezero Crater — for the first time found in igneous rock.  The long-ago environment when the organics were deposited were deemed to have been “habitable.” (NASA/JPL-Caltech/MSSS)

When searching for signs of ancient life on Mars, NASA scientists increasingly focus on organic material — the carbon-based compounds that are the building blocks of life.  Organics were found by the Curiosity rover in Gale Crater, and now new papers report they have also been identified by the instruments of the Perseverance rover in very different kinds of rock in Jezero Crater.

Unlike the Gale Crater organics that were found in sedimentary rocks, these newly found specimens are in igneous rocks — formed when molten rock cools and crystallizes — and are mixed with other compounds known to preserve organics well.

These rock samples are part of the NASA and European Space Agency Mars Sample Return mission, and so they could be brought to Earth in the future for more intensive study. Scientists are excited about what might some day be found.

The new findings about organics and the geology of Jezero Crater are part of a trio of articles in the journal Science published Wednesday.

The lead author of one of the papers, Michael Tice of Texas A&M University, gave this overview of what the Perseverance team is reporting:

“These three papers show that samples collected in the floor of Jezero should be able to tell us a lot about whether living organisms ever inhabited rocks under the surface of the crater over the past several billion years,”  he wrote to me.

The paper he led, Tice said, shows that small amounts of water passed through those rocks at three different times, and that conditions at each of those times could have supported life. “Even more importantly, minerals were formed from the water that are known to be able to preserve organic matter and even fossils on Earth.”

Different kinds of carbon-based organic compounds were viewed within a rock called “Garde” by SHERLOC, one of the instruments on the end of the robotic arm aboard the Perseverance rover. The rover used its drill grind away a patch of rock so that SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) could analyze its interior.

… Read more

Did Ancient Mars Life Kill Itself Off?

October 21, 2022 / / 0 Comments

The study revealed that while ancient Martian life may have initially prospered, it would have rendered the planet’s surface covered in ice and uninhabitable, under the influence of hydrogen consumed by microbes and methane released by them into the atmosphere. (Boris Sauterey and Regis Ferrière)

The presence of life brings many unexpected consequences.

On Earth, for instance, when cyanobacteria spread widely in ancient oceans more than two billion years ago, their production of increasingly large amounts of oxygen killed off much of the other anaerobic life present at the day because oxygen is a toxin, unless an organism  finds ways to adapt.   One of the first global ices followed because of the changed chemistry of the atmosphere.

Now a group of researchers at the University of Arizona has modeled a similar dynamic that could have potentially taken place on early Mars.

As the group reports in the journal Nature Astronomy, their work has found that if microbial life was present on a wetter and warmer ancient Mars — as some now think  that it potentially was — then it would almost certainly have lived below the surface.  The rock record shows that the atmosphere would then have consisted largely of carbon dioxide and hydrogen, which would have warmed the planet with a greenhouse effect.

By using a model that takes into account how processes occurring above and below ground influence each other, they were able to predict the climatic feedback of the change in atmospheric composition caused by the biological activity of these microbes.

In a surprising twist, the study revealed that while ancient Martian life may have initially prospered, its chemical feedback to the atmosphere would have kicked off a global cooling of the planet by the methanogen’s use of the atmospheric hydrogen for energy and the production of methane as a byproduct.

That replacement of hydrogen with methane ultimately would render its surface uninhabitable and drive life deeper and deeper underground, and possibly to extinction.

“According to our results, Mars’ atmosphere would have been completely changed by biological activity very rapidly, within a few tens or hundreds of thousands of years,” said Boris Sauterey, a former postdoctoral student at the University of Arizona who is now a fellow at Sorbonne Université in Paris. .

“By removing hydrogen from the atmosphere, microbes would have dramatically cooled down the planet’s climate.”

Jezero Crater is where the Perseverance rover has been exploring since landing in early 2021.

… Read more

Where Might Plumes of Water Vapor Come From on Icy Moons?

October 12, 2022 / / 0 Comments

This illustration depicts a plume of water vapor that could potentially be emitted from the icy surface of Jupiter’s moon Europa. New research sheds light on what plumes, if they do exist, could reveal about lakes that may be inside the moon’s crust. (NASA/ESA/K. Retherford/SWRI)

It’s been some years since Europa scientists agreed that the Jovian moon has a large global ocean beneath miles of ice.  More recently, scientists have identified what they view as pockets of water surrounded by ice but much nearer the surface than the ocean below.  And there has been research as well into what may be salty, slushy pocket of water further down in the ice covering.

With NASA’s mission to Europa scheduled to launch in about two years, modeling of these all potential collections of liquid water has picked up to prepare for the Europa Clipper arrival to come.

The latest research into what the subsurface lakes on Europa may look like and how they may behave comes in a recently published paper in Planetary Science Journal.

A key finding supports the idea that water could potentially erupt above the surface of Europa either as plumes of vapor or as cryovolcanic activity —  flowing, slushy ice rather than molten lava.

Computer modeling in the paper goes further, showing that if there are eruptions on Europa, they likely come from shallow, wide lakes embedded in the ice and not from the global ocean far below.

“We demonstrated that plumes or cryolava flows could mean there are shallow liquid reservoirs below, which Europa Clipper would be able to detect,” said Elodie Lesage, Europa scientist at NASA’s Jet Propulsion Laboratory and lead author of the research.

“Our results give new insights into how deep the water might be that’s driving surface activity, including plumes. And the water should be shallow enough that it can be detected by multiple Europa Clipper instruments.”

A minimally processed version of this image was captured by JunoCam, the public engagement camera aboard NASA’s Juno spacecraft. It was taken during the mission’s close flyby earlier this fall, almost 950 miles above the moon’s surface. The raw image was processed by “citizen scientist” Navaneeth Krishnan to add enhanced color contrast that allow larger surface features to stand out more.

The question of whether or not Europa has plumes is not settled.  While the plumes coming from Saturn’s moon Enceladus have been well studied and even had a spacecraft fly through one, Europa has only some fuzzy Hubble Space Telescope, Galileo mission and ground-based telescope images that suggest a plume.… 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

Icy Moons, And Exploring The Secrets They Hold

August 18, 2022 / / 0 Comments

Voyager 2’s flew by the Uranian moon Miranda in 1986 and the spacecraft spent 17 minutes taking  photos to make this high-resolution portrait.  Miranda has three oval and trapezoid coronae, tectonic features whose origins remain debated. (NASA / JPL / Ted Stryk)

When it come to habitable environments in our solar system, there’s Earth, perhaps Mars billions of years ago and then a slew of ice-covered moons that are likely to have global oceans under their crusts.  Many of you are familiar with Europa (a moon of Jupiter) and Enceladus (a moon of Saturn) — which have either been explored by NASA or will be in the years ahead.

But there quite a few others icy moons that scientists find intriguing and just possibly habitable.  There is Ganymede,  the largest moon of Jupiter and larger than Mercury but only 40 percent as dense, strongly suggesting a vast supply of water inside rather than rock.

There’s Saturn’s moon Titan, which is known for its methane lakes and seas on the surface but which has a subterranean ocean as well.  There is Callisto, the second largest moon of Jupiter and an subsurface-ocean candidates and even Pluto and Ceres, now called dwarf planets that show signs of having interior oceans.

And of increasing interest are several of the icy moons of Uranus, particularly Ariel and Miranda.  Each has features consistent with a subsurface ocean and even geological activity.  Although Uranus is a distant planet, well past Jupiter and Saturn and would take more than a decade to just get there, the possibility of a future Uranus mission is becoming increasingly real.

The National Academy of Sciences (NAS) Decadal Survey for planetary science rated a Uranus mission as the highest priority in the field, and just today (Aug. 18) NASA embraced the concept.

At a NASA Planetary Science Division town hall meeting, Director Lori Glaze said the agency was “very excited” about the Uranus mission recommendation from the National Academy and that she hoped and expected some studies could be funded and begun in fiscal 2024.

If a Uranus mission is fully embraced,  it would be the first ever specifically to an ice giant system — exploring the planet and its moons.  This heightened interest reflects the fact that many in the exoplanet field now hold that ice giant systems are the most common in the galaxy and that icy moons may well be common as well.… Read more

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