Tag: science

Juno’s next Jupiter fly-by today

9:29 am

Juno is set to make its fourth close fly-by of Jupiter today, dipping to within 2,670 miles of the gas giants cloud tops.

The Juno science team continues to analyze returns from previous flybys. Revelations include that Jupiter’s magnetic fields and aurora are bigger and more powerful than originally thought and that the belts and zones that give the gas giant’s cloud top its distinctive look extend deep into the planet’s interior. Peer-reviewed papers with more in-depth science results from Juno’s first three flybys are expected to be published within the next few months. Also, JunoCam, the first interplanetary outreach camera, is now being guided with the assistance from the public — people can participate by voting for what features on Jupiter should be imaged during each flyby.

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Curiosity’s drill remains out of commission

9:21 am

Ireson Hill

In a science update on Curiosity’s research in Gale Crater, this Science journal article today gives a good overall update on Curiosity’s technical condition.

Since early December 2016, Curiosity hasn’t been able to drill. The problem, likely a stuck brake on the mechanism for extending the drill bit, is serious. “There is apprehension,” says Ashwin Vasavada, Curiosity’s project scientist at the Jet Propulsion Laboratory in Pasadena, California. But the drill still responds intermittently. “We’re not in a situation where it’s completely dead.”

Still, the clock is ticking for the aging rover, and some outside scientists regret not having used a wet chemistry cup. Rocks have punctured its wheels, and the output of its decaying radioactive power source has dropped by 15%. Jack Mustard, a planetary scientist at Brown University, says he understands the team’s hesitancy. But he wished the “mission had moved more quickly with the wet chemistry experiments,” he says. “I am eager to see what we can learn.”

The wet chemistry cup, designed to look for organic life, is an experiment that requires use of the drill but the science team has held off doing. Now it might be too late.

At the moment Curiosity is approaching [see Sol 1598-1599] the small hill that had been to its southwest in my January 18, 2017 update and shown in the image above. I had thought they might make a side trip there on their way up Mount Sharp, and they have, with their actual route taking them around the backside of the hill.

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Plotting the interstellar path to Proxima Centauri

8:40 am

Scientists have calculated the slingshot route that Breakthrough Starshot’s tiny interstellar spacecraft should take in order to reach Proxima Centauri while also gathering the maximum scientific data while zipping past the binary stars of Alpha Centauri.

The solution is for the probe’s sail to be redeployed upon arrival so that the spacecraft would be optimally decelerated by the incoming radiation from the stars in the Alpha Centauri system. René Heller, an astrophysicist working on preparations for the upcoming Exoplanet mission PLATO, found a congenial spirit in IT specialist Michael Hippke, who set up the computer simulations. The two scientists based their calculations on a space probe weighing less than 100 grams in total, which is mounted to a 100,000-square-metre sail, equivalent to the area of 14 soccer fields. During the approach to Alpha Centauri, the braking force would increase. The stronger the braking force, the more effectively the spacecraft’s speed can be reduced upon arrival. Vice versa, the same physics could be used to accelerate the sail at departure from the solar system, using the sun as a photon cannon.

The tiny spacecraft would first need to approach the star Alpha Centauri A as close as around four million kilometres, corresponding to five stellar radii, at a maximum speed of 13,800 kilometres per second (4.6 per cent of the speed of light). At even higher speeds, the probe would simply overshoot the star.

While most of this is hardly revolutionary, this is still the first time anyone has done the hard math based upon a real mission concept.

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U.S. 2020 Mars rover faces delays

9:26 pm

A new inspector general report has pinpointed a number of issues that could cause a delay in the 2020 launch of the next American Mars rover mission.

The biggest risk to the mission, according to NASA OIG, is the sampling system that will be used to collect and store samples of Martian rock and soil that a future mission will gather for return to Earth. That system, an essential part of the mission, has several key technologies that are less mature than planned at this phase of the mission’s development. “The immaturity of the critical technologies related to the Sampling System is concerning because, according to Mars 2020 Project managers, the Sampling System is the rover’s most complex new development component with delays likely to eat into the Project’s schedule reserve and, in the worst case scenario, could delay launch,” OIG stated.

I find it puzzling that the sampling system is an issue. This rover is essentially based on Curiosity, which has very sophisticated equipment for grabbing and even storing samples for periods of time. I don’t understand why such systems could not be quickly revised for future retrieval.

Nonetheless, there are other problems however.

Two instruments on the Mars 2020 mission have also suffered problems. One, called MOXIE, is designed to test the ability to generate oxygen on Mars, saw its estimated increase by more than 50 percent during its development. NASA has taken steps to reduce some of that cost growth by eliminating development of an engineering model and skipping further design improvements in one element of MOXIE.

Another instrument designed to study atmospheric conditions on Mars, MEDA, has suffered delays because of a “financial reorganization” by its developer, Spain’s National Institute for Aerospace Technology. OIG concluded in its report that MEDA is unlikely to be ready for delivery to NASA in April 2018, as currently scheduled. That could require adding MEDA to the rover later in the overall assembly process, or flying the mission without the instrument.

One of the reasons the Obama administration decided to make this 2020 rover mission a reboot of Curiosity was to save cost and development time. Thus, it does not speak well for NASA’s planetary program that they are having these problems.

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Some radioisotope dating might be overestimating the age of samples

7:11 pm

The uncertainty of science: New research suggests the radioisotope dating that scientists use has been overestimating the age of many samples.

The article does not indicate if this overestimate applies to all radioisotope dating or just to the strontium-86/rubidium-87 dating methods mentioned. Nor does the article detail how much of an overestimate the scientists have measured. Depending on these factors the difference — and its influence on scientific results — could be relatively small, or quite large.

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New close-ups of Saturn’s rings

1:00 pm

New close-ups of Saturn’s rings, taken during one of Cassini’s recent ring-grazing orbits, have now been released.

They have released four different images, all at a higher resolution than any previous image. Even so, the individual particles in the rings remain unresolved. Instead, many different intriguing patterns are observed, once again suggesting that though the rings are made of many solid particles, they behave as a unit more like a liquid.

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New measurements of the universe’s expansion rate

3:41 pm

The uncertainty of science: New measurements of the universe’s expansion rate are apparently in agreement with some previous measurements but not with others.

The Hubble constant — the rate at which the Universe is expanding — is one of the fundamental quantities describing our Universe. A group of astronomers, the H0LiCOW collaboration, used the NASA/ESA Hubble Space Telescope and other telescopes in space and on the ground to observe five galaxies in order to arrive at an independent measurement of the Hubble constant. The new measurement is completely independent of — but in excellent agreement with — other measurements of the Hubble constant in the local Universe that used Cepheid variable stars and supernovae as points of reference.

…However, the value measured by Suyu and her team, as well as those measured using Cepheids and supernovae, are different from the measurement made by the ESA Planck satellite. But there is an important distinction — Planck measured the Hubble constant for the early Universe by observing the cosmic microwave background. While the value for the Hubble constant determined by Planck fits with our current understanding of the cosmos, the values obtained by the different groups of astronomers for the local Universe are in disagreement with our accepted theoretical model of the Universe.

Both measurements are very precise, but they do not match, suggesting that there are some basic fundamentals here that astronomers simply do not yet understand.

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Jupiter’s Little Red Spot

9:24 am

Little Red Spot

Cool image time! The image on the right, cropped to show here, is focused in on Jupiter’s Little Red Spot, a storm that formed by the merger of three smaller storms about a decade ago. The cropped image comes from a wider view of Jupiter from Juno that is quite amazing.

Note that the Little Red Spot, while only a third the size the more well known Giant Red Spot, is still about the size of the Earth.

This storm is the third largest anticyclonic reddish oval on the planet, which Earth-based observers have tracked for the last 23 years. An anticyclone is a weather phenomenon with large-scale circulation of winds around a central region of high atmospheric pressure. They rotate clockwise in the northern hemisphere, and counterclockwise in the southern hemisphere. The Little Red Spot shows very little color, just a pale brown smudge in the center. The color is very similar to the surroundings, making it difficult to see as it blends in with the clouds nearby. Citizen scientists Gerald Eichstaedt and John Rogers processed the image and drafted the caption.

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A Saturn moon makes waves

9:57 am

Daphnis makes waves

Cool image time! The image above, taken on January 16, 2017 during one of Cassini’s ring-grazing passes as it enters its last year at Saturn, has been reduced and cropped to post here. It shows clearly the waves caused by the gravity of the moon Daphnis as its travels within a gap in the rings of Saturn.

Daphnis (5 miles or 8 kilometers across) orbits within the 42-kilometer (26-mile) wide Keeler Gap. Cassini’s viewing angle causes the gap to appear narrower than it actually is, due to foreshorteneing. The little moon’s gravity raises waves in the edges of the gap in both the horizontal and vertical directions.

The image also shows many details about Daphnis itself, including a ridge at its equator that is thought to be an accumulation of material gathered from the rings.

The strangeness of Saturn’s rings is well illustrated here. Though made up of many solid particles, as a group the rings act almost like liquid. Note for example the ring on the far side of Daphnis. Its edge gets pulled out slightly as the moon goes by, but then the gravity of the rest of the ring pulls it back.

The universe is a wonderful place, as it is. No need to make up stuff (such as faces on Mars or fake civilizations on the Moon), as our imagination is probably insufficient to match the weirdness that is really out there.

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Trump’s 1st NASA appointees suggest future policy

9:49 am

A memo released January 20 from NASA’s acting administrator accepting the job also announced the first Trump appointees to NASA. The history and policy positions of those two appointees I think once again give us a very clear indication of where NASA might be going in the coming years.

[Acting administrator Robert] Lightfoot, in the memo, said that the administration has appointed Erik Noble to serve as White House senior advisor and Greg Autry to be White House liaison. The two are the first members of the so-called “beachhead team” of administration staffers assigned to NASA, at least on a short-term basis.

Autry is an assistant professor of entrepreneurship at the University of Southern California who has been a proponent of commercial space activities. Autry was one of eight members of the agency review team, or “landing team,” assigned to NASA by the transition office of then President-elect Trump.

Noble did not serve on the landing team, but worked on the Trump campaign as a political data analyst. Noble, who earned a Ph.D. in environmental studies from the University of Colorado, spent seven years at the NASA Goddard Institute of Space Studies in New York, working on weather and climate models. [emphasis mine]

Autry, believes strongly in private space, and has also been a critic of SLS/Orion. Being placed at NASA as Trump’s first appointee strongly suggests that a Trump administration is going to accelerate the commercial space push that was begun by the Bush administration and then strongly supported by the Obama administration. It also suggests that the SLS and Orion projects are going to face a difficult future and will likely be phased out.

Noble’s appointment is more important. As a former scientist at the Goddard Institute, he is now well positioned to possibly appoint a new head to that organization, or even become its head himself. The present person in charge there, Gavin Schmidt, has increasingly become suspect as a scientist, instead appearing more as global warming political advocate. Since he took over that Institute, the climate data there has been increasingly tampered with, with past data being cooled and recent data being warmed, thus creating the impression that the Earth’s climate has been warming more than indicated by all previous research. Schmidt’s explanations for these “adjustments” (the term he uses) have never been satisfactory. He then uses the results from these “adjustments” to make annual press releases declaring each year as the “hottest” ever, though the raw data shows no such thing.

Even if Noble does not replace Schmidt, Noble appears well positioned to force Schmidt to either finally justify his data adjustments, or remove them from the data stream so that the raw data will be allowed to dominate policy decisions once again.

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Planes flying at high latitudes can travel through clouds of high cosmic radiation

10:14 pm

The uncertainty of science: Researchers have found evidence that suggests that planes flying at higher latitudes can sometimes fly through concentrated pockets of high cosmic radiation.

“We have flown radiation sensors onboard 264 research flights at altitudes as high as 17.3 km (56,700 ft) from 2013 to 2017,” says Kent Tobiska, lead author of the paper and PI of the NASA-supported program Automated Radiation Measurements for Aerospace Safety (ARMAS). “On at least six occasions, our sensors have recorded surges in ionizing radiation that we interpret as analogous to localized clouds.”

…Conventional wisdom says that dose rates should vary smoothly with latitude and longitude and the height of the aircraft. Any changes as a plane navigates airspace should be gradual. Tobiska and colleagues have found something quite different, however: Sometimes dose rates skyrocket for no apparent reason. “We were quite surprised to see this,” says Tobiska.

All of the surges they observed occurred at relatively high latitudes, well above 50 degrees in both hemispheres. One example offered in their paper is typical: On Oct 3, 2015, an NSF/NCAR research aircraft took off from southern Chile and flew south to measure the thickness of the Antarctic ice shelf. Onboard, the ARMAS flight module recorded a 2x increase in ionizing radiation for about 30 minutes while the plane flew 11 km (36,000 feet) over the Antarctic Peninsula. No solar storm was in progress. The plane did not abruptly change direction or altitude. Nevertheless, the ambient radiation environment changed sharply. Similar episodes have occurred off the coast of Washington state.

The theories proposed to explain this at the link are not very convincing, and suggest to me that they really do not know what causes this. All we do know is that it likely associated with the interaction of the Earth’s magnetic field and cosmic radiation.

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Mars rover update: January 18, 2017

3:37 pm

Curiosity

Curiosity's location, Sol 1582

For the overall context of Curiosity’s travels, see Pinpointing Curiosity’s location in Gale Crater.

In the past month, since my last rover update on December 22, 2016, Curiosity has begun moving again, carefully picking its way through the dune-filled flats in the foothills at the base of Mount Sharp. The route taken, shown on the image on the right, corresponds to the easternmost of the possible routes I noted in my November 14, 2016 update. This route is also the most direct route, which I think is smart considering that the rover’s life on Mars certainly uncertain and the higher they can climb the more geological information they will get.

I have also annotated the likely route into the near future, including a possible side trip to the base of the mesa up ahead. It appears to me that they are now a little more than halfway through the flats, with Mt. Sharp directly ahead, as shown by the panorama below, taken near the end of December. The goal is a canyon just out of view to the right of this panorama.

Looking at Mount Sharp

The flats the rover is presently traversing, and visible in the foreground of the panorama above, is strewn with dark sand that often piled into large sand dunes. Where the ground is exposed, it is made up of a scattering of pavement-like rocks. As noted in a press release yesterday, many of these flat rocks have polygonal cracks and boxwork similar to that seen in dried mud here on Earth, suggesting that this area was once wet and then dried. This geology helps confirm the theory of planetary scientists that Gale Crater was once filled with water that slowly evaporated away. As the rover climbs, it leaves the lakebed and begins to move through the lake’s various shores, each one older than the last.

Opportunity

For the overall context of Opportunity’s travels at Endeavour Crater, see Opportunity’s future travels on Mars.
» Read more

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Akatsuki discovers a giant wave in Venus’ upper atmosphere

9:18 am

The Japanese Venus probe Akatsuki has discovered a giant persistent wave in the planet’s upper atmosphere that almost spans its entire face.

This week, researchers from Japan Aerospace Exploration Agency (JAXA) published infrared and ultraviolet images of Venus, taken by their Akatsuki orbiter between December 7 and 11, 2015, in Nature Geoscience. Akatsuki’s pictures reveal a curved region roughly 6000 miles long (Venus’ entire diameter is just around 7,500 miles) with a higher temperature than the surrounding atmosphere. How did the curved “smile” fight those high winds to remain in place for all four days of observation?

The answer may lie in a phenomenon very familiar to Earthlings. Gravity waves, not to be confused with gravitational waves, form when gravity pushes and pulls at the seam between two different materials. Waves on the ocean are perhaps the most obvious example—they exist where the sea meets the sky. But gravity waves also show up in the air, where wind flows over mountains to form waves that undulate upward through different layers of the atmosphere.

The mystery here is that scientists do not have a mountain chain that could have caused this giant Venusian wave. Moreover, it was there in 2015 but they haven’t seen it since.

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Cause of vision problems in space pinpointed?

9:12 am

New research suggests that scientists have pinpointed the cause of the vision problems astronauts experience from long term weightlessness.

The new research showed that intracranial pressure in zero-gravity conditions, such as exists in space, is higher than when people are standing or sitting on Earth, but lower than when people are sleeping on Earth. The researcher’s finding suggests that the constancy of pressure on the back of the eye causes the vision problems astronauts experience over time.

More important, the research has also suggested a possible cure.

“The information from these studies is already leading to novel partnerships with companies to develop tools to simulate the upright posture in space while astronauts sleep, thereby normalizing the circadian variability in intracranial pressure, and hopefully eliminating the remodeling behind the eye,” said Dr. Levine, who holds the Distinguished Professorship in Exercise Sciences.

The researchers have continued studying whether it is possible to lower intracranial pressure by means of a vacuum device that pulls blood away from the head. They previously showed that a negative pressure box that snuggly fits the lower body can lower intracranial pressure when applied for 20-minute periods. They will soon be testing the effect of the lower body negative pressure device on eye remodeling when negative pressure is applied for eight-hour periods. “Astronauts are basically supine the entire time they are in space. The idea is that the astronauts would wear negative pressure clothing or a negative pressure device while they sleep, creating lower intracranial pressure for part of each 24 hours,” said first author Dr. Justin Lawley, Instructor in Internal Medicine at UT Southwestern and a researcher at the IEEM.

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Curiosity spots cracks formed from drying mud

5:27 pm

mud cracks on Mars?

As Curiosity moves across the dust-shrewn dune-filled flats at the base of Mt. Sharp it has recently taken images of surface rocks that have cracks resembling those found from drying mud.

Scientists used NASA’s Curiosity Mars rover in recent weeks to examine slabs of rock cross-hatched with shallow ridges that likely originated as cracks in drying mud. “Mud cracks are the most likely scenario here,” said Curiosity science team member Nathan Stein. He is a graduate student at Caltech in Pasadena, California, who led the investigation of a site called “Old Soaker,” on lower Mount Sharp, Mars.

If this interpretation holds up, these would be the first mud cracks — technically called desiccation cracks — confirmed by the Curiosity mission. They would be evidence that the ancient era when these sediments were deposited included some drying after wetter conditions. Curiosity has found evidence of ancient lakes in older, lower-lying rock layers and also in younger mudstone that is above Old Soaker.

The rover is no longer on the floor the crater, but in the foothills at the base of Mt. Sharp. Thus, what we are likely looking at is evidence of the slow disappearance of the giant lake that scientists think once filled Gale Crater. These mud cracks suggest that the rover is now moving up out of the lake and through its margins.

I plan to do a rover update for both Curiosity and Opportunity tomorrow, so stay tuned.

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Preparing to dive into Saturn’s rings

9:35 am

Saturn from above

Cool image time! The photo at the right, reduced to show here, was taken by Cassini on October 28, 2016 as it was shifting its orbit to prepare for the spacecraft’s last year at Saturn, where it will make repeated dives down past and even inside the gas giant’s rings. As they note at the link,

No Earth-based telescope could ever capture a view quite like this. Earth-based views can only show Saturn’s daylit side, from within about 25 degrees of Saturn’s equatorial plane. A spacecraft in orbit, like Cassini, can capture stunning scenes that would be impossible from our home planet.

It is interesting to compare this image with this July image. Comparing the two provides a sense of Cassini’s travels.

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NASA asteroid redirect mission delayed again

11:15 pm

Due to the uncertainty of its budget NASA has decided to delay the award of the contracts to begin work on its asteroid redirect mission (ARM).

The uncertainty is that Congress has never budgeted any real money for it. The mission was proposed by Obama but only vaguely, without any real support. First it was to be a manned mission to an asteroid, using Orion. Then it was to be an unmanned mission to bring a large asteroid closer to Earth to be later visited by astronauts in an Orion capsule. Then the large asteroid became a mere boulder, with the manned mission delayed until the unforeseen future.

I think NASA sees the writing on the wall here. They expect this vague unsupported mission to die with the next administration, and have decided it is better not to waste money on it now.

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The raging storms of Jupiter’s south pole

9:55 am

Cool image time! Below the fold I have embedded an animation that was assembled from 30 Juno images taken during its third orbital close approach of Jupiter. It is at first a little hard to watch, which is why I have not made it visible on the main page, but it is worth watching because it gives a real sense of how powerful and violent the storms are in the polar regions of the gas giant planet. Keep your eye especially glued to the storms near the center of the image. In a very short time that it took Juno to zip past Jupiter, less than a day, these storms rotated about one third. Remember too that each storm would probably cover at least half of the Earth’s surface.

We desperately need a fleet of weather satellites orbiting Jupiter to give us a continuous view of these storms. The knowledge gained about atmospheric weather patterns would be priceless.

» Read more

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Utah climate scientists whine about possible NASA cuts

9:31 am

The squealing of pigs: In the kind of journalistic pro-government spending propaganda that I despise, the Salt Lake Tribune today published this article giving climate scientists in their local area a platform to lobby the public in favor of their NASA funding.

The article provides a quick quote from a Trump campaign official noting their strong hostility to the politicization of climate research, and then spends the rest of the article allowing scientist after scientist to condemn that position and to defend that spending, repeatedly implying that should the NASA cuts go through, the research will end and even possibly that access to the data from NASA climate satellites will be denied to the public and to the scientists. At no time does the article provide any thoughtful information to explain that Trump administration perspective, which is based on some reasonable and very justifiable concerns.

I note this article as a warning. Expect more of this very bad journalism. Most of the press are blindly liberal and Democratic Party partisans. They are going to work blindly with the climate community to help them defend their funding, without the slightest effort at objective reporting. The public should be aware of this, and see this political lobbying for what it is.

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The status of telescopes the NSF is getting rid of

9:08 am

Back in 2012 the National Science Foundation (NSF) proposed that it cease funding a slew of older, smaller telescopes in order to use that money to fund the construction and operation of newer more advanced facilities. This article, focused on the fate of the Arecibo Observatory in Puerto Rico, provides a nice table that shows the status of these telescopes.

The options were either to find new funding, be mothballed, or even demolished. It appears that most of the telescopes in question have found new funding and will remain in use in some manner. The one telescope that has apparently failed to obtain any additional funding from others is the McMath–Pierce Solar Telescope on Kitt Peak in Arizona, which when built in 1962 was the world’s largest solar telescope, an honor for which it is still tied.

In 2015 I had written an article for Sky & Telescope about how these budget cuts were effecting the telescopes on Kitt Peak. At that time the people in charge of McMath-Pierce were hunting for new support but were coming up short. Almost two years later it appears that their hunt has been a failure, and the telescope will likely be shut down, and possibly demolished.

It will be a sad thing if McMath-Pierce is lost, but I am not arguing to save it. If its observational capabilities were truly valuable and needed by the scientific community than someone would have come forward to finance it. That no one has suggests that the money really can be spent more usefully in other ways.

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Could Tabby’s Star have eaten a planet?

8:50 am

A new theory has been proposed by astronomers to explain the unprecedented dimming of Tabby’s Star, and it isn’t an alien civilization.

If Tabby’s star devoured a planet in the past, the planet’s energy would have made the star temporarily brighten, then gradually dim to its original state. The bigger the planet was, the longer the star would take to dim. Depending on the size of the planet, this event could have happened anywhere between 200 and 10,000 years ago.

As the planet fell into its star, it could have been ripped apart or had its moons stripped away, leaving clouds of debris orbiting the star in eccentric orbits. Every time the debris passes between us and the star, it would block some light, making the star seem to blink.

If true, this theory would suggest that such events can happen more than scientists has expected. Moreover, this theory can be tested during future observations when the star experiences its next dimming.

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The sunspot crash continues

3:49 pm

On Sunday NOAA posted its monthly update of the solar cycle, covering sunspot activity for December. As I do every month, I am posting it here with annotations to give it context.

December 2016 Solar Cycle graph

January 2017 sunspots as of January 9, 2017

The graph above has been modified to show the predictions of the solar science community. 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.

Sunspot activity continues to decline, and it appears to be declining at a steadily faster rate as the solar cycle ramps down towards minimum. Not only did sunspot activity drop below the 2007 low prediction in 2016, since 2017 began the sun has been blank almost continuously, as shown by the graph on the right. The signs continue to point to a solar minimum occurring much sooner than predicted, producing an unprecedented short and weak solar cycle.

Despite this, the appearance in December of the first sunspot for the next solar cycle suggests that we will not be entering a Grand Minimum in the coming decades. It does not guarantee it, as there is some evidence that even though no sunspots were visible during the Maunder Minimum in the 1600s the magnetic activity that causes sunspots did continue, and with our better observation equipment today we may see sunspots they would not have seen in the 1600s.

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Herschel Crater on Mimas

10:00 am

Herschel Crater on Mimas

Cool image time! The photo on the right was taken by Cassini on October 22, 2016 when the spacecraft was about 115,000 miles away and has a resolution of about 3,300 feet per pixel. It highlights well Mimas’ most distinctive feature, its single gigantic crater, which also makes the tiny moon of Saturn one of the more distinctive planetary bodies in the entire solar system.

Named after the icy moon’s discoverer, astronomer William Herschel, the crater stretches 86 miles (139 kilometers) wide — almost one-third of the diameter of Mimas (246 miles or 396 kilometers) itself.

Large impact craters often have peaks in their center — see Tethys’ large crater Odysseus in The Crown of Tethys. Herschel’s peak stands nearly as tall as Mount Everest on Earth.

The mystery here is how did Mimas survive such an impact. One would think that the moon would be been split apart by the collision, and that it didn’t suggests the material involved was soft enough to absorb the dynamic forces, and that the speed of the impact was slow enough to reduce those forces overall.

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The Earth and Moon, as seen from Mars

1:00 pm

The Earth and Moon as seen from Mars

Cool image time! The image above, a composite of four separate Mars Reconnaissance Orbiter pictures, was taken on November 20, 2016.

Each was separately processed prior to combining them so that the moon is bright enough to see. The moon is much darker than Earth and would barely be visible at the same brightness scale as Earth. The combined view retains the correct sizes and positions of the two bodies relative to each other.

The reddish region on Earth is Australia, with Antarctica the bright white area below that.

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Hubble takes a look at both Voyagers’ interstellar path

10:43 am

Using the Hubble Space Telescope astronomers have taken a peek at the interstellar material that the two Voyager spacecraft will travel through as they move out and leave the solar system in the coming decades.

Voyager 1 is 13 billion miles from Earth, making it the farthest human-made object ever built. In about 40,000 years, after the spacecraft will no longer be operational and will not be able to gather new data, it will pass within 1.6 light-years of the star Gliese 445, in the constellation Camelopardalis. Its twin, Voyager 2, is 10.5 billion miles from Earth, and will pass 1.7 light-years from the star Ross 248 in about 40,000 years.

For the next 10 years, the Voyagers will be making measurements of interstellar material, magnetic fields, and cosmic rays along their trajectories. Hubble complements the Voyagers’ observations by gazing at two sight lines along each spacecraft’s path to map interstellar structure along their star-bound routes. Each sight line stretches several light-years to nearby stars. Sampling the light from those stars, Hubble’s Space Telescope Imaging Spectrograph measured how interstellar material absorbed some of the starlight, leaving telltale spectral fingerprints.

Hubble found that Voyager 2 will move out of the interstellar cloud that surrounds the solar system in a couple thousand years. The astronomers, based on Hubble data, predict that the spacecraft will spend 90,000 years in a second cloud before passing into a third interstellar cloud.

This is very clever science. It allows data from Hubble to complement the data from the two Voyager spacecraft to better understand the interstellar regions that surround our solar system.

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Could Venus’ atmospheric dark streaks be life? Mission proposes to find out

10:00 am

A clever mission concept, proposed as a joint Russian/U.S. unmanned probe to Venus, would use a solar-powered unmanned aerial vehicle (UAV) to fly through the atmosphere for at least a year in order to try to find out the nature of the planet’s atmospheric mysterious dark streaks.

Descending hypersonically into the atmosphere after detaching from the orbiter, the UAV would be filled with hydrogen or helium gas, keeping it buoyant at a nominal floating altitude of 50 kilometers, allowing it to glide through the clouds while moving through the night-time hemisphere. Upon daylight, the solar-powered propellors would kick in and raise the craft’s altitude to around 60 kilometers.

Over the course of three to four days, the craft could move around the planet along the upper atmosphere’s ‘super-rotation,’ the strange phenomenon where the atmosphere seems to be uncoupled from the solid planet and rotates much faster. The UAV would therefore be able to explore the clouds at different altitudes, moving from air mass to air mass, from regions with UV absorbers to regions devoid of them, sampling and measuring the composition of the atmosphere.

The dark streaks, first photographed when Mariner 10 flew past on February 5, 1974 and took more than four thousand pictures, are made of a still unknown material in the upper clouds that absorbs ultraviolet light. The scientists of this mission concept propose that these dark streaks could even be Venusian life.

Finding life at high altitude in the atmosphere of a planet would make sense. After all, microbes have been found at similar heights in Earth’s atmosphere. The challenge for life on Venus is the planet’s extreme temperature. The surface, at 462º C (864º F), is hot enough to melt lead, and the surface pressure of 92 bar is the equivalent of being almost a kilometer under water.

However, in a region beginning around 50 kilometers in altitude and extending a dozen kilometers outward is a sweet spot where the temperature ranges between 30ºC and 70ºC (86ºF to 158ºF) and the pressure is similar to Earth’s surface. Life could potentially survive in this zone where the dark-streaking UV absorber is found.

Intriguingly, the sulfuric acid droplets within the clouds aren’t necessarily a show-stopper to life. Earlier Venera missions detected elongated particles in the lower cloud layer that are about a micron long, about the width of a small bacterium. These particles could be coated in ring-shaped polymers of eight sulphur atoms, called S8 molecules, which are known to exist in Venus’ clouds and which are impervious to the corrosive effects of sulfuric acid. Furthermore, S8 absorbs ultraviolet light, re-radiating it in visible wavelengths. If the particles are microbes, they could have coated themselves in S8, making them resistant to the corrosive effects of sulfuric acid. It has even been postulated that the S8 exists as a result of microbial activity.

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