Tag: science

A deep dive into Valles Marineris

2:56 pm

Dunes on the floor of Valles Marineris
Click for full image.

The vastness of Mars is sometimes hard to fathom. While the planet is much smaller than Earth, its entire global surface is approximately the same as the Earth’s land area. This is a lot of territory. It took humanity many tens of thousands of centuries to expand outward to settle all of it. It took even longer before humanity was successfully able to map all of the Earth so that its entire surface was known to all humans, a task that was only completed a handful of centuries ago.

While we now have the technology to quickly map the entire globe of a planet like Mars, the devil is always in the details. At this time the resolution of our global maps give us only a glimpse of the Martian surface.

The image to the right, reduced and cropped to post here, is a good example. Taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 30, 2019, it shows a set of large dunes on the northern floor of a side canyon on Mars that is part of Coprates Chasma, a canyon that forms only a small part of the vast Valles Marineris canyon system east of the giant volcanoes of the Tharsis Bulge.

The sand of these dunes is mostly volcanic material, dark basalt that was deposited as lava from those giant volcanoes, then later ground down in landslides and erosion to be recycled as sand that formed dunes trapped within the canyon bottom. The dunes themselves are slowly moving eastward, driven mostly by the predominate west-to-east winds that blow down this side canyon of Coprates Chasma. The motion is very slow, so slow that even though the image title is “Coprates Chasma Dune Changes”, I was unable to spot any changes when I compared this 2019 image with a photo taken in June 2019.

To find out what had changed, I contacted Matt Chojnacki of the Lunar and Planetary Laboratory at the University of Arizona, who has been studying the nature of the sand dunes in Valles Marineris. After making a quick preliminary blink test using more sophisticate tools than I have available, he found “minor advancements. The rocks move a bit too in places.” Without a full analysis he also added, “I can tell some dune crests have moved to the east.”

The research by Chojnacki and others has found that the dunes within Valles Marineris are in many ways different than dunes found elsewhere in the mid-latitudes on Mars, suggesting that being trapped within this giant canyon has produced some specific regional features. They tend to be darker, the canyon contains several sand dune seas, called ergs (only seen elsewhere on Mars in the polar regions), and the dunes tend to be more hardened, so that they change relatively little when compared to similar dunes elsewhere on Mars.

These particular dunes in Coprates Chasma however are not hardened, since if so they would have been covered by the landslides and material that comes down from the canyon’s nearby northern slopes. Instead, they move, but appear to move far slower than similar dunes elsewhere on Mars.

To me, this image provides a good vehicle for getting a sense of the size of Valles Marineris. Coprates Chasma itself only one of about a dozen named sections of the entire Valles Marineris canyon system, and this particular image shows only the floor of a side canyon of Coprates. The map below gives an overview of the entire system.
» Read more

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Movie of Jupiter’s south pole storms

9:03 am

Clip from animation of Jupiter's south polar storms

Cool image time! Citizen scientist Gerald Eichstädt has used images taken by Juno of Jupiter’s south polar storms to produce an animation that shows the evolution of those storms over a short time period.

The movie is more a computer model than an assemblage of images.

A fluid dynamical 2D model rotating with Jupiter’s System III rotation rate is started with a map of PJ19 (Juno’s 19th close approach) vorticity measurements of the south polar region between 75 and 90 degrees south (azimuthal, equidistant, planetocentric) as initial condition. The vorticity map is based on a sequence of PJ19 JunoCam images.

Relative vorticities are encoded in color, blue for cyclonic, orange for anticyclonic relative vorticity. The animated gif covers 48 hours, with one frame per real-time hour. Played with 25 fps, the result is a 90,000-fold time-lapsed animation.

I have embedded the animation below the fold. It is quite impressive.
» Read more

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Buried glaciers flowing off of Martian mesa

1:55 pm

Glacial flow off of mesa
Click for full image.

Cool image time! Planetary geologists now think that the mid-latitudes of Mars contain many buried and inactive glaciers, formed several million years ago when the planet’s inclination was more than 50 degrees [pdf], rather than the 25 degrees it is now. At that time the mid-latitudes were actually colder than the poles, and water would sublimate from the poles to the colder mid-latitudes to pile up as snow and glaciers.

With today’s 25 degree inclination those mid-latitude glaciers are inactive, and have been so for several million years. It might even be that Mars’ water is beginning a shift back to the poles, but this is uncertain. If anything the planet is presently in a balance, and won’t start transferring water back to the poles until its inclination drops closer to zero.

The image to the right, taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on September 23, 2019, is of one of those glacial flows, coming off a mesa in a region called Protonilus Mensae, located in the transition zone between the southern highlands and the northern lowland plains where an intermittent ocean might have once existed.

Much of the geology of Protonilus Mensae is chaos terrain, places where the surface has eroded along angled fissures to form many mesas. The overview map below focuses in on the particular mesa where this flow is located. The red boxes indicate all the MRO images taken of this mesa, with the image above indicated by the black dot.
» Read more

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Megadunes in the giant canyon of Mars’ north polar icecap

1:02 pm

Martian megadunes at the beginning of summer
Click for full image.

Cool image time! The photo to the right, cropped and reduced to post here, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on September 15, 2019, right at the beginning of summer at the north polar icecap of Mars.

Without a larger context it is very difficult to figure out what this image shows. The image title, “Seasonal Changes of Chasma Boreale Megadunes,” gives us some basic clues. The streaks of black and dark grey are giant dunes, with this image showing their trailing edge. The darkest streaks are likely places where the thin winter mantle of dry ice has begun to sublimate away with the coming of spring, exposing the darker sand dunes below. The surrounding flat white areas are either the permanent water ice of the icecap or the surface of the lowland northern plains that surround that icecap.

The montage below shows a series of monitoring photos, beginning in 2018 during the last Martian summer and continuing through the start and middle of the spring and ending with the photo above. It shows the seasonal evolution of that upper carbon dioxide dry ice mantle, which reveals the darker dunes below as that dry ice mantle sublimates away.
» Read more

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Martian impacts and streaks

12:18 pm

Slope-streaked crater on Mars
Click for full image.

In the most recent image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO), there was the cool image to the right, reduced and cropped to post here, of a crater that appeared to have hundreds and hundreds of slope streaks along its inner slopes.

Slope streaks are quite mysterious. They are found in the equatorial regions as dark (though sometimes light) streaks on steep slopes, appearing throughout the year and slowly fading over time. They also appear to be a geological phenomenon unique to Mars. Nothing on Earth or any other planet appears to correspond.

As such, their nature and cause remains unknown, though there are a bunch of theories, with the most popular being that these are a kind of dust avalanche. They are always found in connection with dust-covered terrain, but they also make no significant topological change to the surface, other than brightness.

The slope streaks in this crater are especially intriguing, because of the number of streaks. In digging further into the MRO archive I found a number of images of this crater and its surrounding terrain. It appears that sometime before 2012 there was a relatively recent impact close to the exterior of the eastern rim of this crater. The image below, taken in 2014 by MRO, shows this impact as the large dark splotch, with the new crater indicated by the arrow..
» Read more

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North magnetic pole continues its drift

3:52 pm

The uncertainty of science: The newest 2020 version of the World Magnetic Model, released on December 10, 2019, shows that the north magnetic pole is continuing its unprecedented drift eastward and away from the Canadian Arctic.

A new and updated version of the WMM is released every five years. The latest WMM2020 model will extend to 2025.

Since Earth’s magnetic field is created by its moving, molten iron core, its poles aren’t stationary and they wander independently of each other. Since its first formal discovery in 1831, the north magnetic pole has traveled around 1,400 miles (2,250 km). This wandering has been generally quite slow, allowing scientists to keep track of its position fairly easily. Since the turn of the century, this speed has increased.

The WMM2020 forecasts that the northern magnetic pole will continue drifting toward Russia, although at a slowly decreasing speed—down to about 40 km per year compared to the average speed of 55 km over the past twenty years.

Though we know the magnetic field is produced by the magnetism related to the Earth’s molten iron core, scientists do not have a solid understanding of the details, including why the drift of the pole has accelerated this century as well as shifted eastward.

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The importance of small telescopes to science and civilization

10:58 am

The main cluster of telescopes, on Mount Lemmon
Largest cluster of telescopes on Mount Lemmon, six visible with three just out of view.

On December 11, 2019 I was kindly given a personal tour by Alan Strauss, director of the Mount Lemmon Sky Center, of the telescopes located on the mountaintops of the Santa Catalina Mountains overlooking Tucson. Strauss runs the educational outreach program for the University of Arizona astronomy department and the Steward Observatory, both of which operate the mountaintop facility.

The telescopes, numbering almost a dozen, are in two groups, two telescopes on the peak of Mount Bigelow and the rest clustered on the higher peak of Mount Lemmon. None are very gigantic by today’s standards, with their primary mirrors ranging in size from 20- to 61-inches. For comparison, the largest operating telescope in the world on the Canary Islands is 409 inches across. Hubble has a 94-inch mirror. And the new giant telescopes under design or being built have mirrors ranging from 842 inches (Giant Magellan) to 1,654 inches (European Extremely Large Telescope).

Thus, the small telescopes in the Santa Catalinas generally don’t make the news. They are considered passe and out-of-date, not capable of doing the kind of cutting edge astronomy that all the coolest astronomers hunger for.

Yet, without them, we likely would not have future astronomers. » Read more

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Scientists reject discovery of biggest known black hole

9:20 am

The uncertainty of science: In three new papers published this week astronomers have found that the announced discovery in early December of the biggest super-massive black hole ever found, 70 times the mass of the Sun, does not hold up.

In a recent study (a peer-reviewed study published Nov. 27), a team of scientists reported the discovery of the binary system LB-1, which contains a star and, according to the findings, a black hole companion 70 times the mass of our sun. This was major news, a stellar-mass black holes (black holes formed by the gravitational collapse of a star) are typically less than half that massive. But while the study, led by Jifeng Liu, of the National Astronomical Observatory of China (NAOC) of the Chinese Academy of Sciences, was exciting, it was also wrong.

Three new papers came out this week that reexamined the findings from Liu’s study, and these studies say that LB-1’s black hole isn’t actually all that massive.

The new papers find that a closer look at the data finds that it wasn’t doing what the initial researchers thought.

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Maven makes first map of Mars’ high altitude winds

9:11 am

High altitude wind patterns on Mars

Scientists using the Martian orbiter Maven have produced the first global map of the high altitude wind circulation of Mars.

The measurements of winds that were recently mapped above Mars were found at an altitude range of about 140-240 kilometers (85-150 miles) above the planet’s surface.

The wind data has been gathered by the Neutral Gas and Ion Mass Spectrometer (NGIMS). NGIMS’ original purpose was to determine the structure and composition of the Martian atmosphere by measuring in it the amounts of ions (electrically charged particles) and gases. However, although it was not originally designed to do so, in April 2016, the MAVEN team began using NGIMS to observe horizontal winds. Pausing normal collection of data, scientists on Earth programmed the instrument to nod back and forth so that it could detect the direction of winds along its track.

By combining data from many tracks as MAVEN orbits Mars, scientists slowly built up a map of wind behavior. This led to a startling discovery: the wind patterns actually correlated with the Martian topography below.

They have found that even at this high altitude the winds shift around the high volcanoes of the Tharsis Bulge.

To my eye, the wind pattern seen in the image, taken from the video at the link, is remarkably similar to the global wind patterns found on Venus, forming a widening V-pattern moving from east to west. Though the two are vastly different, the similarity is quite intriguing.

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Interacting galaxies

8:42 am

Interacting galaxies
Click for full image.

Astronomers using the 8-meter Gemini Telescope on Mauna Kea today released a new image of the Heron galaxy, showing its interaction with a nearby neighbor.

The new image captures the slow and intimate dance of a pair of galaxies some 160 million light-years distant and reveals the sparkle of subsequent star formation fueled by the pair’s interactions.

The two galaxies, astronomers have concluded, have already “collided” at least once. However, galactic collisions can be a lengthy process of successive gravitational encounters, which over time can morph the galaxies into exotic, yet unrecognizable forms. These galaxies, as in all galactic collisions, are engaged in a ghostly dance as the distances between the stars in each galaxy preclude actual stellar collisions and their overall shapes are deformed only by each galaxy’s gravity.

One byproduct of the turbulence caused by the interaction is the coalescence of hydrogen gas into regions of star formation. In this image, these stellar nurseries are revealed in the form of the reddish clumps scattered in a ring-like fashion in the larger galaxy (and a few in the smaller galaxy). Also visible is a dusty ring that is seen in silhouette against the backdrop of the larger galaxy. A similar ring structure is seen in this previous image from the Gemini Observatory, likely the result of another interacting galactic pair.

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New storm spotted at Jupiter’s south pole

8:31 am

New cyclone at Jupiter's south pole
Click for full image.

New images from Juno have revealed the formation of a new Texas-sized cyclone joining the circle of storms around Jupiter’s south pole.

In the infrared Juno image to the right, the new storm is the small bright cyclone in the lower right.

[D]uring Juno’s 22nd science pass [on November 3], a new, smaller cyclone churned to life and joined the fray. “Data from Juno’s Jovian Infrared Auroral Mapper [JIRAM] instrument indicates we went from a pentagon of cyclones surrounding one at the center to a hexagonal arrangement,” said Alessandro Mura, a Juno co-investigator at the National Institute for Astrophysics in Rome. “This new addition is smaller in stature than its six more established cyclonic brothers: It’s about the size of Texas. Maybe JIRAM data from future flybys will show the cyclone growing to the same size as its neighbors.”

Probing the weather layer down to 30 to 45 miles (50 to 70 kilometers) below Jupiter’s cloud tops, JIRAM captures infrared light emerging from deep inside Jupiter. Its data indicate wind speeds of the new cyclone average 225 mph (362 kph) – comparable to the velocity found in its six more established polar colleagues.

Because of Juno’s orbit we do not get continuous views of the gas giant’s cloud-tops, so we can’t see the moment-by-moment evolution of these storms, which makes it impossible to obtain a full understanding of their formation or disappearance. Even then it will likely take centuries of observations to even begin to get a fuller understanding of the meteorology of Jupiter.

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New Hubble images of Comet 2I/Borisov

12:17 pm

Comet 2I/Borisov taken by Hubble prior to and at its closest approach to Sun
Click for full image.

Scientists today released new images taken by the Hubble Space Telescope of the interstellar object Comet 2I/Borisov. The image on the left was taken prior to the comet’s closest approach to the Sun, while the image on the right was taken during that closest approach. The vertical smeared object to the left in the earlier image is a galaxy that happened to be in the field of view. The blue color of both images is a false color to bring out details.

“Hubble gives us the best upper limit of the size of comet Borisov’s nucleus, which is the really important part of the comet,” said David Jewitt, a UCLA professor of planetary science and astronomy, whose team has captured the best and sharpest look at this first confirmed interstellar comet. “Surprisingly, our Hubble images show that its nucleus is more than 15 times smaller than earlier investigations suggested it might be. Our Hubble images show that the radius is smaller than half-a-kilometer. Knowing the size is potentially useful for beginning to estimate how common such objects may be in the solar system and our galaxy. Borisov is the first known interstellar comet, and we would like to learn how many others there are.”

The first image was taken from a distance of 203 million miles, while the second was taken from 185 million miles. Expect more images in late December, when the comet makes its closest approach to Earth at a distance of 180 million miles.

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OSIRIS-REx team picks primary sample site

12:03 pm

Four candidate landing sites
Click for full image.

The OSIRIS-REx science team has picked the site they have dubbed Nightingale as the primary landing site where they will attempt to obtain a sample from the asteroid Bennu in the summer of 2020. The back-up site is Osprey at the equator.

I have embedded the replay of the NASA live stream of the press event below the fold. The first 21 minutes of the video are an overview of the mission, leading up to the announcement by Dante Lauretta, OSIRIS-REx’s principal investigator. He notes then that the site “does have some hazards” but they chose it for its “scientific value.” While its higher latitude location has some advantages, it also makes it more difficult for landing. The one large boulder there, which Lauretta calls “Mt Doom,” also carries risk for the touch-and-go operations.

The back-up site, Osprey, is on the equator with less hazards, but will present more problems obtaining the tiny-sized particles the sample grab equipment was designed to get.

Not that this matters, but if I have been in a betting pool I would have won, since Nightingale has been my guess for which site they’d pick since early November.
» Read more

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A new map of the water ice on Mars

9:45 am

Annotated water ice map of Mars
Click for full resolution image.

In a new science paper planetary scientists have produced a new global map of the water ice of Mars, based on data from Mars Reconnaissance Orbiter (MRO) and Mars Odyssey.

The image above is a lower resolution version of that map, annotated by me. The black areas are regions covered with a thicker layer of dust, so no good data was obtained. As you go from red to green to blue to purple the ice is thought to be closer to the surface, with the depth as small as an inch in the dark purple areas. The white rectangular represents the region best for human settlement, as it has ice near the surface and is at lower latitudes.

The red box indicates the location in Arcadia Planitia that is SpaceX’s candidate landing zone for Starship. Based on this new water ice map it appears that SpaceX has chosen very well. And the scientists who wrote this paper agree, as noted in the press release: “A large portion of a region called Arcadia Planitia is the most tempting target in the northern hemisphere.”

The map also confirms the existence of the 30 to 60 degree latitude bands where scientists believe a lot of buried glaciers exist. Both bands are both very evident in this new map.

To provide some further context, below is a global map of Mars labeled to show its major geographic features as well as the locations of all previous and upcoming landers/rovers, rearranged to match the water ice map above.
» Read more

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How the Mars2020 rover differs from Curiosity

1:00 pm

A JPL press release today outlines some of the main engineering differences between Curiosity, the rover that has been exploring Gale Crater for the past fifteen years, and Mars2020, the unnamed rover that will be launched in July 2020 to explore Jezero Crater

One of the major the engineering improvements, based on what was learned with Curiosity, are the Mars2020 wheels:

Curiosity has prepared Mars 2020’s team for “off-roading” on the Red Planet. When holes began appearing in the veteran rover’s aluminum wheels, engineers realized that sharp rocks cemented on the Martian surface exert more pressure on the wheels than expected. Careful drive planning, along with a software upgrade, will keep them in shape for the rest of Curiosity’s journey up Mount Sharp.

While Mars 2020’s wheels are made from the same materials, they’re slightly bigger and narrower, with skins that are almost a millimeter thicker. Instead of Curiosity’s chevron-pattern treads, or grousers, Mars 2020 has straighter ones and twice as many per wheel (48 versus 24). Extensive testing in JPL’s Mars Yard has shown these treads better withstand the pressure from sharp rocks but work just as well on sand.

The computer and software has also been upgraded to speed daily operations. In addition, the new rover will have 23 cameras, six more than Curiosity, all of which will be capable of producing color images. And most important, the drill will be larger and will drill cores for obtaining samples that will be stored for possible return by a later mission.

The landing is set for February 18, 2021. If all goes well this rover will be exploring the Martian surface well in to the 2030s.

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Sunspot update Nov 2019: The longest flatline in centuries

5:53 pm

The Sun is now in what appears to be the longest stretch ever recorded, since the 11-year solar sunspot cycle reactivated in the 1700s after the last grand minimum, of sunspot inactivity. This record-setting dearth of practically no sunspots has now stretched to six months in a row.

On December 8 NOAA released its November update of its graph showing the long term sunspot activity of the Sun. As I have done now every month since this webpage began in 2011, I have posted it below, with annotations:

November 2019 sunspot activity
The graph above has been modified to show the predictions of the solar science community for the previous solar maximum. The green curves show the community’s two original predictions from April 2007, with half the scientists predicting a very strong maximum and half predicting a weak one. The red curve is their revised May 2009 prediction, extended in November 2018 four years into the future.

In November the Sun saw two official sunspots (here and here) and one active area that never received an official sunspot number, with two of these three weak events having a polarity linking them to the next solar maximum.
» Read more

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The dark splotches on Mars: Magnets for dust devils

3:38 pm

Olympus Maculae, land of dark splotches

One of the numerous geological mysteries that planetary scientists have discovered among the many high resolution images taken by the various Martian orbiters are a series of dark splotches, ranging in diameter from one to fifteen miles, running in an east-west line on the lower western slopes of the giant volcano Olympus Mons.

Scientists have dubbed this string of splotches Olympus Maculae and, because of their superficial resemblance to the islands of Hawaii, have labeled each splotch, or macula, after those islands, as shown in the overview map above, created by geologist Kirby Runyon of the Applied Physics Lab in Maryland as part of a presentation [pdf] given at a science conference in September 2019.

Prior to the 2018 global dust storm on Mars scientists were not quite sure what caused these dark patches. The data suggested the maculae were less dusty than the surrounding terrain, but why this was so was not clear.

The advent of that storm however gave them a chance to get before and after photos. In October 2018 I found several images in monthly download of new images from the high resolution camera of Mars Reconnaissance Orbiter (MRO) and posted them, making a vain attempt to locate what had changed. As I wrote,

I found that MRO has taken images of this location twice before, in 2007 and in 2009. I spent about fifteen minutes trying to find something that had changed, but was unable to locate anything, other than what look like a few wind-blown streaks probably caused by dust devils. I suspect I do not know what to look for.

I then made some guesses about what caused these splotches, all wrong I have since learned.

Since then more images of these splotches have been downloaded from MRO, all once again indicating that changes have been detected. Below is a sequence of images of the splotch dubbed Ka’ula, the first taken in 2008, the second in 2018 just after the global dust storm, and the third in 2019, one year after the storm. Set side-by-side the changes are more obvious.
» Read more

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Cloud stream on Jupiter

9:21 am

Cloud stream on Jupiter
Click for full image.

Cool image time! The photo to the right, taken by Juno on November 3, was enhanced by citizen scientist Björn Jónsson to bring out the colors. It shows a band of repeating large storms, with tiny white thunderheads popping up within them.

The dark areas at the edges of the swirls are likely not an aspect of the clouds but shadows created because the white swirls sit higher than the surrounding gases.

Sadly the press release does not give us a scale. The image was taken from a distance of 3,200 miles. I suspect each cloud swirl would likely cover much of the Earth.

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OSIRIS-REx completes reconnaissance of four candidate sample sites

10:04 am

Four candidate landing sites
Click for full image.

OSIRIS-REx has completed its high resolution reconnaissance of the four candidate sites on the asteroid Bennu, chosen for possible sample capture during touch-and-go operations planned for the summer of 2020.

In the next few days the science team will decide which of these four sites, shown above, will be the primary and back-up landing locations. The decision however appears challenging, based on the information gathered.

Bennu has also made it a challenge for the mission to identify a site that won’t trigger the spacecraft’s safety mechanisms. During Recon A, the team began cataloguing Bennu’s surface features to create maps for the Natural Feature Tracking (NFT) autonomous navigation system. During the sample collection event, the spacecraft will use NFT to navigate to the asteroid’s surface by comparing the onboard image catalog to the navigation images it will take during descent. In response to Bennu’s extremely rocky surface, the NFT system has been augmented with a new safety feature, which instructs it to wave-off the sampling attempt and back away if it determines the point of contact is near a potentially hazardous surface feature. With Bennu’s building-sized boulders and small target sites, the team realizes that there is a possibility that the spacecraft will wave-off the first time it descends to collect a sample.

Based on the information at the link, plus the presentation by Dante Lauretta, OSIRIS-REx’s principal investigator, given at the asteroid conference I attended in November, I suspect that Nightingale will be primary landing site.

Regardless, it appears the science team has recognized that the landing will difficult, and will likely require multiple attempts before the spacecraft’s navigation system lets it happen.

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