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Category: Our Solar System (page 2 of 8)

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

Reports From Inside the Sun’s Corona

July 11, 2022 / / 1 Comment

This movie is built from images taken over 10 days during the full perihelion encounter when the spacecraft was nearing the Sun’s corona. The perihelion is a brief moment during the encounter time, when the spacecraft is at its closest point to the Sun. The movie is from orbit 10 and dates and distances are on the frames, and changing locations of planets are in red.  (AHL/JHU; NASA)

To borrow from singer Paul Simon, these are definitely days of miracles and wonders — at least when it comes to exploring and understanding our Sun.

The Parker Solar Probe has been swinging further and further into the Sun’s corona, having just finished its 12th of 24 descents into a world of super-heated matter (plasma) where no human creation has ever gone.

The probe has dipped as close as 5.3 million miles from the surface of the sun — Mercury is 32 million miles from that solar surface — and is flying through the solar wind, through streamers (rays of magnetized solar material)  and even at times through coronal mass ejections, those huge eruptions of magnetized plasma flying at speeds up to nearly 2,000 miles per second.

This is all a goldmine for solar scientists, an opportunity to study our star — and by extension all stars — up close and to learn much more about how it works.

At a four-day conference at the Johns Hopkins University Applied Physics Lab late last month, scores of scientists described the results of their early observations and analyses of the measurements and images coming from the Parker Probe via its The Wide-Field Imager (WISPR) and instruments that measure energy and magnetic flows.  The results have often surprising and, as some scientists said, “thrilling.”

“Parker Solar Probe was developed to answer some of the biggest puzzles, biggest questions about our Sun,” said Nour Raouafi, project scientist for the Parker Solar Probe.

“We have learned so much that we believe we are getting close to finding some important answers.  And we think the answers will be quite big for our field, and for science.”

The Parker Solar Probe had observed many switchbacks in the corona— traveling disturbances in the solar wind that cause the magnetic field to bend back on itself.  They are an as-yet unexplained phenomenon that might help scientists uncover more information about how the solar wind is accelerated from the Sun. (NASA’s Goddard Space Flight Center/Conceptual Image Lab/Adriana Manrique Gutierrez)

Among the many unexpected solar features and forces detected by the Parker Probe is the widespread presence of switchbacks, rapid flips of the Sun’s magnetic field moving away from the Sun. … 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

A Clue Into The Makeup of Jupiter’s Moon Europa Provided by the Greenland Ice Sheet

April 25, 2022 / / 0 Comments

Double ridge ice formations seen on Europa are similar to formations detected on the Greenland Ice Sheet. This artist’s rendering shows how double ridges on the surface of Jupiter’s moon Europa may form over shallow, refreezing water pockets within the ice shell. This mechanism is based on the study of an analogous double ridge feature found on Earth’s Greenland Ice Sheet. (Justice Blaine Wainwright)

Europa’s ice crust is crossed by thousands of double ridges, pairs of long parallel raised lines with a small valleys in between, sometimes as much as hundreds of miles long and skyscraper-height tall rims. While these double ridges are ubiquitous on Europa’s surface, how they form remains something of a mystery to scientists.

Dustin Schroeder, an associate professor of geophysics at Stanford University’s School of Earth, Energy & Environmental Sciences, was working on an issue related to climate change when he saw double ridges similar to those seen on Europa here on Earth.  The ridges, in Northwest Greenland, were tiny when compared with those on Europa, but the found the same “M”-shaped crest as found everywhere on that Jovian moon.

“We were working on something totally different related to climate change and its impact on the surface of Greenland when we saw these tiny double ridges – and we were able to see the ridges go from ‘not formed’ to ‘formed,’ ” Schroeder said.

Could the double ridges be forming as a result of processes similar to those that form the double ridges on Europa?

If so, then Greenland would provide a possibly important new window into a central question about Europa:  Is that thick ice shell surrounding the subsurface ocean completely solid, or does it have what are called “water sills” within the shell?

This is important because, as the Nature Communications paper concludes, “If the same process is responsible for Europa’s double ridges, our results suggest that shallow liquid water is spatially and temporally ubiquitous across Europa’s ice shell.”

Or as Schroeder put it, “If the mechanism we see in Greenland is how these things happen on Europa, it suggests there’s water everywhere,” he said in a release.

They can make this inference because the double ridges formed in Greenland are the known, and detectable, result of the dynamics of subsurface water surrounded by the ice sheet.

Surface imagery comparison of a double ridge on Europa (a) and on Earth (b), on the Northwest Greenland Ice Sheet.

… Read more

“Nature Has Become More Beautiful.” Physicist Eugene Parker and his Life Unlocking Secrets Of The Sun

April 12, 2022 / / 0 Comments

 

Parker with an image of the solar corona, the outermost portion of Sun’s atmosphere.  Parker brought new understanding to the nature and workings of the corona and the solar wind, which originates in the corona. (University of Chicago)

When  Eugene Parker was 16 years old,  he decided he didn’t want to spend the summer hanging out in suburban Detroit.  So Parker went up to the state capital looking to buy some tax delinquent land held by the state.

He selected a 40-acre piece of woods in far-off Cheboygan County, not far from Mackinac Island.  There was nothing on the land but trees.  He bought it with $120 from his own earlier summertime earnings.

Over the next three summers, Parker, his younger brother and sometimes a cousin and a friend constructed a log cabin on the land.  Because this was during World War II and gas was strictly rationed,  they couldn’t ask their parents for a ride up, and so they often bicycled the more than 300 miles to their homestead.

The cabin still doesn’t have electricity or indoor running water, but it has been used regularly by Parker and his family for almost 80 years.  And in many ways, that cabin reflects the basic character, the drive and the profound originality of the boy who built it and went on to become one of the great theoretical physicists of the 20th century.

The young Parker atop a birch  tree in 1943, on the site where his northern Michigan cabin would be built. (Courtesy of the Parker family.)

Eugene Parker, who passed away earlier this month at 94, has been hailed as the father of solar physics and is perhaps best known as the man who — basically single-handedly and despite many eminent critics –came up with the theory of the “solar wind,” a torrent of charged particles and magnetic fields that always and in all directions is blasting out from the Sun.

Parker’s innumerable achievements in his field, as well as his old-school civility and demeanor, earned him the first and only honor of its kind given by NASA — having a major space mission named after him while alive.

Ailing and aged 91, he nonetheless went with his family down to Florida in 2018 to watch the launch of the Parker Solar Probe — an extraordinary mission that flies through the blast furnace of the Sun’s corona in its effort to learn more about the origins of the solar wind and the forces at play that produce that still mysterious solar corona.… Read more

Venus, as Never Seen Before

February 15, 2022 / / 0 Comments

The darkside of Venus, as imaged by an optical and near infrared camera on NASA’s Parker Solar Probe. (NASA)

For the first time, the surface of Venus has been imaged in visible wavelengths from space. The camera on the Parker Solar Probe pierced through the thick Venusian cloud cover and captured blurred but extremely valuable images of the highlands and lowlands of the planet.

The breakthrough images came thanks to a spacecraft with an entirely different mission — the Parker Probe, which has been exploring and progressively nearing the Sun in unprecedented ways.  And to get ever closer, it uses trips around Venus to slow down and thereby fly closer to the Sun.

It was during two of those trips around Venus in 2000 and 2001 that the Parker camera, which sees in visible and near infrared wavelengths, was able to  image the night side of Venus.  This was a first and totally unexpected, since Venus is known to have a dense cover of clouds.

The planet is also, of course, stunningly hot, with a mean temperature of 867 degrees Fahrenheit on the surface.  But the temperatures are lower on the elevated Aphrodite Terra, the largest highland region on the Venusian surface, and that is the area that shows as being dark in the images.

“Venus is the third brightest thing in the sky, but until recently we have not had much information on what the surface looked like because our view of it is blocked by a thick atmosphere,” said Brian Wood, lead author on the new study in Geophysical Research Letters and a physicist at the Naval Research Laboratory in Washington.  “Now, we finally are seeing the surface in visible wavelengths for the first time from space.”

The presentation below, put together by NASA, the John’s Hopkins University Applied Physics Lab and Naval Research Lab, is a stitched together video of the Parker Probe’s  Feb. 20, 2021 pass by the dark side of the planet.

Clouds of sulfur dioxide and sulfuric acid obstruct most of the visible light coming from Venus’ surface and so observing from both the ground and from space has relied on radar and observing wavelengths in the infrared that can pierce through the clouds.

But on two passes, the the Parker Probe’s Wide-field Imager for Solar Probe (WISPR) picked up a range of wavelengths from 470 nanometers to 800 nanometers. Some of that light is the near-infrared – wavelengths that we cannot see, but sense as heat – and some is in the visible range, between 380 nanometers and about 750 nanometers.… Read more

Can We Trust a Handful of Grains to Tell Us About the Early Earth? A Look at the Hayabusa2 Asteroid Sample

February 13, 2022 / / 0 Comments
The Hayabusa2 sample return capsule returning to Earth. The bright streak in the sky is the capsule, shock heated as it enters the Earth’s atmosphere. The bright lights on the ground are buildings. (JAXA)

In the early hours of December 6, 2020, what appeared to be a shooting star blazed across the sky above the Woomera desert in South Australia. The source was the sample return capsule from JAXA’s Hayabusa2 mission, which contained precious material from a near-Earth asteroid known as Ryugu.

Within 60 hours, the capsule had been retrieved and flown to the curation facility at JAXA’s Institute of Space and Astronautical Science in Japan. In vacuum conditions to prevent any trace of contamination, the capsule was opened to reveal over 5 grams of asteroid grains.

This material is expected to have undergone little change since the early days of the solar system some 4.5 billion years ago, and its highly anticipated analysis could provide new information about how the Earth acquired water and organics needed to begin life. The sample is the first ever collected from a carbonaceous (C-type) asteroid, which resemble primitive meteorites found to have a chemical composition close to that of the Sun.

Tet despite a rigorously planned and executed journey of over 5,000 million kilometers to bring back a pristine sample from space, concerns have remained. Chief among these are whether the rocky grains in the sample capsule were typical of the asteroid.

If the Hayabusa2 spacecraft had inadvertently gathered grains from an unusual spot, or if the grains had been altered during the collection and return to Earth, then deductions about the asteroid’s composition–and therefore our solar system’s past–could be wrong.  

The sample from asteroid Ryugu (from Yada et al. Nature Astronomy 2021)

The Hayabusa2 team had already gone to rather extreme lengths to mitigate this issue.

In addition to the rapid retrieval operation that ensured that the sample was not contaminated by our planet’s atmosphere, the spacecraft had performed the dangerous landing twice on the surface of asteroid Ryugu to collect samples from two separate sites.

One of these locations was close to where the spacecraft had made an artificial crater, ejecting material from beneath the asteroid’s surface to be gathered during the second collection operation. Rocky grains from below the top layer surface are expected to be particularly pristine, as they have been protected from the bombardment of sunlight, cosmic rays and micrometeorites.… Read more

A Huge Watery Reservoir May Lie Beneath the Surface of The “Grand Canyon” of Mars

December 22, 2021 / / 0 Comments

The Valles Marineris in equatorial Mars and is one of the the largest canyon in the solar system.  It is surpassed in length only by the rift valleys of Earth. (NASA)

That early Mars was much wetter and warmer than it is today has been well established by numerous missions.  Water ice is visible at the poles and many fossil rivers have been found in the southern highlands of Mars.  The Curiosity rover found as well that the large crater where it landed — Gale Crater – once had a lake and in-flowing streams.

But the presence of water, or proof that water once flowed, has been missing in the equatorial latitudes  of the planet.

However, now a paper based on data from the European/Russian Trace Gas Orbiter (TGO) strongly suggests that the Candor Chasma, located near the heart of the massive canyon system called Valles Marineris, has either large deposits of a kind of permafrost water ice just below its surface or of rocks formed in water and now containing that H2O in their structure.

The article to appear in the journal Icarus says that the discovery of large amounts of hydrogen in the region speaks of this aqueous  past.

“We found a central part of Valles Marineris to be packed full of water – far more water than we expected,” Alexey Malakhov, of the Russian Space Research Institute and a co-author of the study, said in a statement.

“This is very much like Earth’s permafrost regions, where water ice permanently persists under dry soil because of the constant low temperatures.”

 

Valles Marineris, seen at an angle of 45 degrees to the surface in near-true color and with four times vertical exaggeration. The image covers an area of about 400,000 square miles. The largest portion of the canyon, which spans right across the image, is known as Melas Chasma. Candor Chasma is the connecting trough immediately to the north. The digital terrain model was created from 20 images taken by the High Resolution Stereo Camera of the Mars Express Orbiter. (ESA)

Valles Marineris is 10 times longer and 4 times deeper than our Grand Canyon.  Geologists have theorized that Valles Marineris began to open along geological faults about 3.5 billion years ago. The faulting may have been caused by the tectonic activity that accompanied the growth of the giant volcanoes in Tharsis, lying just to the west.… Read more

Metal Mini-Asteroids Detected Passing Near Earth, Offering Potentially Great Science and Maybe Future Mining

November 3, 2021 / / 0 Comments

An artist impression of a close flyby of the metal-rich Near-Earth asteroid 1986 DA. Astronomers using the NASA Infrared Telescope Facility have confirmed that the asteroid is made of 85% metal. (Addy Graham/University of Arizona)

Metal asteroids offer something rare in the solar system — the core of a planet without all the rock that normally surrounds it.

Since it is impossible to directly examine a planetary or lunar core if the parent body remains intact, metal-rich asteroids where the upper mantle and crust layers have been lost to a cataclysmic crash offer a potential path to, in effect, peek inside the depths (and deep time) of an object.

The asteroid Psyche is such an object, and that’s why NASA approved a mission to the asteroid that is scheduled to launch next year.  Orbiting the sun between Mars and Jupiter in the largest asteroid belt, Psyche appears to be the exposed nickel-iron core of an early planet, and as such reveals the early evolution of our solar system.

But Psyche is not the only metal-rich asteroid known to astronomers, and it certainly is not the closest.

Two much smaller “mini-Pysches” have been detected that are also comprised of iron, nickel, and other metals ranging from platinum to rare earth elements.  And these two mini-asteroids — 1986 DA and 2016 ED85 — were recently found to have their spectral signatures are quite similar to asteroid Psyche.

And unlike Psyche, which is between 180 million and 360 million miles away, these mini-Psyches orbit less than twenty million from Earth every 20 to 30 years.

“These kind of metal-rich Near-Earth asteroids are extremely rare,” said Vishnu Reddy of the University of Arizona, and co-author of a recent paper in Planetary Science Journal.  “There are some 27,000 known Near-Earth objects, and only these two are metal rich.  Of the 1.2 million asteroids that have been identified, only a little over a dozen are in that metal-rich category.”

Reddy  has been part of a group researching unusual near-Earth objects since 2005, and so these findings are most rewarding.

“In the years ahead we can study Psyche, a large metal-rich object that is quite far away,” Reddy said.  “And now we also know of two much smaller metal-rich objects that are also much, much closer to us.”

Artist’s conception of Psyche, with orbiter spacecraft.  The mission, led by Linda Elkins-Tanton at Arizona State University, is scheduled to launch next year. 

… Read more

Frigid Europa Holds a Huge and Maybe Habitable Ocean Beneath Its Thick Ice Covering. How is That Possible?

September 29, 2021 / / 2 Comments

Europa has one of the smoothest surface of any body in the solar system.  A moon as old as Europa that did not have an ice cover — and a likely ocean inside — would be pocked with asteroid craters.  On Europa, these craters appear to be absorbed into the icy surface via geologic and thermal processes.  Giant lakes trapped in Europa’s crust also bust up the icy surface. (NASA)

Jupiter’s moon Europa is almost five times as far away from the sun as Earth is, with surface temperatures that don’t rise above minus 260 degrees Fahrenheit.  It’s slightly smaller than our moon and orbits but 400,000 miles from the solar system’s largest planet, which it takes but 3.5 Earth days to orbit.  As a result it is tidally locked, always showing the same face to Jupiter.

When it comes to potentially habitable objects in our solar system, Europa would not seem to be a terribly likely possibility.

But, of course, it is.  And in three years NASA’s Europa Clipper mission will launch to explore what would appear to be one of the most unlikely yet possible places in our solar system to find potential signs of life.

The reason why is that scientists are almost certain that under Europa ‘s 10-to 15 mile ice covering is a deep, global ocean of salty water.

The size of the ocean has not been well determined yet, with estimates of between 40 and 100 miles of depth.  But a  consensus has been reached that the ocean is likely to be global, and contains two to three times as much liquid water as found on Earth.

This then raises a question with great significance for Europa, other moons in the solar system and quite likely planets and moons well beyond us:  How can there be so much liquid water inside such frigid places?

The spot toward the lower left is one Europa, against the backdrop of Jupiter.  Images from Voyager in 1979 bolster the modern hypothesis that Europa has an underground ocean and is therefore a good place to look for extraterrestrial life. The dark spot on the upper right is a shadow of another of Jupiter’s large moons. Sixteen frames from Voyager 1’s 1979 Jupiter flyby were recently reprocessed and merged to create this image.  (NASA, Voyager 1, JPL, Caltech; Processing & License: Alexis Tranchandon / Solaris)

There are numerous possible answers to that question, and it’s likely that all or most played some role.… Read more

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