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vox_mundi

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Re: Astronomical news
« Reply #400 on: October 19, 2020, 04:19:58 PM »
Spacecraft Design Could Get to Titan in Only 2 years Using a Direct Fusion Drive
https://phys.org/news/2020-10-spacecraft-titan-years-fusion.html



The concept fusion drive, called a direct fusion drive (or DFD), is in development at the Princeton Plasma Physics Laboratory (PPPL). Scientists and Engineers there, led by Dr. Samuel Cohen, are currently working on the second iteration of it, known as the Princeton field reversed configuration-2 (PFRC-2). Eventually, the system's developers hope to launch it into space to test, and eventually become the primary drive system of spacecraft traveling throughout the solar system.

Though still under development, the engine itself exploits many of the advantages of aneutronic fusion, most notably an extremely high power-to-weight ratio. The fuel for a DFD drive can vary slightly in mass and contains deuterium and a helium-3 isotope. Even with relatively small amounts of extremely powerful fuel, the DFD can outperform the chemical or electric propulsion methods that are commonly used today. The specific impulse of the system, which is a measure of how effectively an engine uses fuel, is estimated to be comparable to electrical engines, the most efficient currently available. In addition, the DFD engine would provide 4-5 N of thrust in low power mode, only slightly less than what a chemical rocket would output over long periods of time. Essentially, the DFD takes the excellent specific impulse of electric propulsion systems and combines it with the excellent thrust of chemical rockets, for a combination that melds the best of both flight systems.



All of those improved specifications are great, but in order to be useful, they actually have to get a spacecraft somewhere. The paper's authors picked Titan, largely because it's relatively far away, but also extremely interesting due to its liquid cycles and abundant organic molecules.

Spacecraft performance, planetary alignments and orbital mechanics resulted in two different potential paths, one where constant thrust was only applied at the beginning and the end of the journey (called a thrust-coast-thrust—TCT—profile) and one in which the thrust was constant for the duration of the journey.

Both journeys involved switching the direction of thrust to slow the spacecraft down to enter into the Saturnian system. Providing constant thrust would put the journey at a little less than two years, while the TCT profile would result in a total trip duration of 2.6 years for a spacecraft much larger than Cassini. Both of those paths would not require any gravity assists, which spacecraft traveling to the outer planets have regularly benefited from.

... With all the orbital mechanics out of the way and the spacecraft safely in Titan's orbit, it can begin to take advantage of another of the DFD's benefits—it can provide direct power to the spacecraft's systems. Most outer solar system missions rely on radioisotope thermal generators (RTGs) for their power source. But a DFD is, in fact, a power source in addition to being a source of thrust. If designed correctly, it could provide all the power a spacecraft needs for an extended mission lifespan.



Trajectory design for a Titan mission using the Direct Fusion Drive:
https://webthesis.biblio.polito.it/15184/1/tesi.pdf
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Tom_Mazanec

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Re: Astronomical news
« Reply #401 on: October 19, 2020, 05:12:13 PM »
Two years to Titan is good, but what would be a game changer is a reasonable time to 550 AU from the sun, to take advantage of the solar gravitational focus.
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vox_mundi

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Re: Astronomical news
« Reply #402 on: October 21, 2020, 01:58:15 PM »
NASA Probe OSIRIS-REx 'Boops' Asteroid Bennu In Historic Mission
https://phys.org/news/2020-10-nasa-probe-osiris-rex-boops-asteroid.html



After a four-year journey, NASA's robotic spacecraft OSIRIS-REx briefly touched down on asteroid Bennu's boulder-strewn surface on Tuesday to collect rock and dust samples in a precision operation 200 million miles (330 million kilometers) from Earth.

... If OSIRIS-REx successfully comes home in September 2023, it will have collected the largest sample returned from space since the Apollo era.

... Scientists want at least 60 grams but the spacecraft is capable of picking up as much as two kilograms, or five pounds.

If it turns out the spacecraft didn't collect enough, it will have another go on January 12, 2021, at a backup site which is another relatively boulder-free area near the rock's equator.

https://www.nasa.gov/osiris-rex
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Tor Bejnar

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Re: Astronomical news
« Reply #403 on: October 21, 2020, 10:45:16 PM »
Quote
... Scientists want at least 60 grams but the spacecraft is capable of picking up as much as two kilograms, or five pounds.
On Earth, 2 kg ~ 5 lb., but on the asteroid, way less than a pound (link).  (2 kg on Pluto is about 0.3 lbs.)
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vox_mundi

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“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

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Sigmetnow

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Re: Astronomical news
« Reply #405 on: October 22, 2020, 02:57:13 AM »
Quote
... If OSIRIS-REx successfully comes home in September 2023, it will have collected the largest sample returned from space since the Apollo era.

But we’ll be collecting and returning lots of moon regolith before then. 
Probably.

“The sampling event brought the spacecraft all the way down to sample site Nightingale, touching down within three feet (one meter) of the targeted location.”  8)
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vox_mundi

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Re: Astronomical news
« Reply #406 on: October 24, 2020, 07:36:23 AM »
NASA’s OSIRIS-REx Spacecraft Collects Significant Amount of Asteroid
https://www.nasa.gov/press-release/nasa-s-osiris-rex-spacecraft-collects-significant-amount-of-asteroid




Two days after touching down on asteroid Bennu, NASA’s OSIRIS-REx mission team received on Thursday, Oct. 22, images that confirm the spacecraft has collected more than enough material to meet one of its main mission requirements – acquiring at least 2 ounces (60 grams) of the asteroid’s surface material.

The spacecraft captured images of the sample collector head as it moved through several different positions. In reviewing these images, the OSIRIS-REx team noticed both that the head appeared to be full of asteroid particles, and that some of these particles appeared to be escaping slowly from the sample collector, called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) head. They suspect bits of material are passing through small gaps where a mylar flap – the collector’s “lid” – is slightly wedged open by larger rocks.

The images also show that any movement to the spacecraft and the TAGSAM instrument may lead to further sample loss. To preserve the remaining material, the mission team decided to forego the Sample Mass Measurement activity originally scheduled for Saturday, Oct. 24, and canceled a braking burn scheduled for Friday to minimize any acceleration to the spacecraft.

From here, the OSIRIS-Rex team will focus on stowing the sample in the Sample Return Capsule (SRC), where any loose material will be kept safe during the spacecraft’s journey back to Earth.

https://www.theguardian.com/science/2020/oct/23/nasa-spacecraft-osiris-rex-asteroid-rubble
« Last Edit: October 24, 2020, 07:41:31 AM by vox_mundi »
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vox_mundi

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Re: Astronomical news
« Reply #407 on: October 26, 2020, 05:53:24 PM »
NASA’s SOFIA Discovers Water on Sunlit Surface of Moon
https://www.nasa.gov/press-release/nasa-s-sofia-discovers-water-on-sunlit-surface-of-moon/



NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) has confirmed, for the first time, water on the sunlit surface of the Moon. This discovery indicates that water may be distributed across the lunar surface, and not limited to cold, shadowed places.

SOFIA has detected water molecules (H2O) in Clavius Crater, one of the largest craters visible from Earth, located in the Moon’s southern hemisphere. Previous observations of the Moon’s surface detected some form of hydrogen, but were unable to distinguish between water and its close chemical relative, hydroxyl (OH). Data from this location reveal water in concentrations of 100 to 412 parts per million – roughly equivalent to a 12-ounce bottle of water – trapped in a cubic meter of soil spread across the lunar surface. The results are published in the latest issue of Nature Astronomy.

As a comparison, the Sahara desert has 100 times the amount of water than what SOFIA detected in the lunar soil. Despite the small amounts, the discovery raises new questions about how water is created and how it persists on the harsh, airless lunar surface.


Clavius Base - 2001: A Space Odyssey

https://www.nature.com/articles/s41550-020-01222-x

-----------------------------------------------

Tiny Moon Shadows May Harbor Hidden Stores of Ice
https://phys.org/news/2020-10-tiny-moon-shadows-harbor-hidden.html

Hidden pockets of water could be much more common on the surface of the moon than scientists once suspected, according to new research led by the University of Colorado Boulder. In some cases, these tiny patches of ice might exist in permanent shadows no bigger than a penny.

"If you can imagine standing on the surface of the moon near one of its poles, you would see shadows all over the place," said Paul Hayne, assistant professor in the Laboratory of Atmospheric and Space Physics at CU Boulder. "Many of those tiny shadows could be full of ice."

In a study published today in the journal Nature Astronomy, Hayne and his colleagues explored phenomena on the moon called "cold traps"—shadowy regions of the surface that exist in a state of eternal darkness at -260°F.

Drawing on detailed data from NASA's Lunar Reconnaissance Orbiter, the researchers estimate that the moon could harbor roughly 15,000 square miles of permanent shadows in various shapes and sizes—reservoirs that, according to theory, might also be capable of preserving water via ice. Previous studies estimated less than 7000 square miles.

Moon water has been eyed as a potential resource by NASA, which created a program named Artemis in 2019, to send American astronauts back to the moon this decade. Launching water to space costs thousands of dollars per gallon. Future explorers may be able to use lunar water not only to quench their own thirst but to refuel their rockets.

Micro cold traps on the Moon, Nature Astronomy (2020).
https://www.nature.com/articles/s41550-020-1198-9

---------------------------------------

« Last Edit: October 26, 2020, 06:10:53 PM by vox_mundi »
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vox_mundi

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Re: Astronomical news
« Reply #408 on: October 26, 2020, 07:55:45 PM »
Study Offers More Complete View of Massive Asteroid Psyche
https://phys.org/news/2020-10-view-massive-asteroid-psyche.html



A new study authored by Southwest Research Institute planetary scientist Dr. Tracy Becker discusses several new views of the asteroid 16 Psyche, including the first ultraviolet observations. The study, which was published today in The Planetary Science Journal and presented at the virtual meeting of the American Astronomical Society's Division for Planetary Sciences, paints a clearer view of the asteroid than was previously available.

... "We've seen meteorites that are mostly metal, but Psyche could be unique in that it might be an asteroid that is totally made of iron and nickel," Becker said. "Earth has a metal core, a mantle and crust. It's possible that as a Psyche protoplanet was forming, it was struck by another object in our solar system and lost its mantle and crust."

Becker observed the asteroid at two specific points in its rotation to view both sides of Psyche completely and delineate as much as possible from observing the surface at ul-traviolet (UV) wavelengths.

"We were able to identify for the first time on any asteroid what we think are iron oxide ultraviolet absorption bands," she said. "This is an indication that oxidation is happen-ing on the asteroid, which could be a result of the solar wind hitting the surface."

Becker's study comes as NASA is preparing to launch the spacecraft Psyche, which will travel to the asteroid as part of an effort to understand the origin of planetary cores. The mission is set to launch in 2022. Metal asteroids are relatively rare in the solar system, and scientists believe Psyche could offer a unique opportunity to see inside a planet.



Tracy M. Becker et al, HST UV Observations of Asteroid (16) Psyche, The Planetary Science Journal (2020).
https://iopscience.iop.org/article/10.3847/PSJ/abb67e
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Tom_Mazanec

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Re: Astronomical news
« Reply #409 on: October 27, 2020, 11:56:58 AM »
Extreme 'Black Widow' Star Identified as Source of Mystery Gamma Radiation
https://www.sciencealert.com/extreme-record-breaking-black-widow-star-is-the-source-of-mystery-gamma-radiation
Quote
Now, astronomers have solved the mystery and pinned down that second star by searching gamma-ray data obtained between 2008 and 2018. Together, the two stars constitute one of the weirdest binary systems we've ever seen.

"The binary star system and the neutron star at its heart, now known as PSR J1653-0158, set new records," said astronomer Lars Nieder of the Albert Einstein Institute Hannover in Germany.

"We have discovered the galactic dance of a super heavyweight with a flyweight: At slightly more than twice the mass of our Sun, the neutron star is extraordinarily heavy. Its companion has about six times the density of lead, but only about 1 percent the mass of our Sun.

"This 'odd couple' orbits every 75 minutes, more quickly than all known comparable binaries."
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vox_mundi

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Re: Astronomical news
« Reply #410 on: October 27, 2020, 01:23:26 PM »
Massive Asteroid Subject of New Findings
https://phys.org/news/2020-10-massive-asteroid-subject.html

A University of Hawaiʻi Institute for Astronomy (IfA) astronomer has revealed critical new findings linked to a large asteroid expected to pass extremely close to Earth. Dave Tholen and collaborators have announced the detection of Yarkovsky acceleration on the near-Earth asteroid Apophis. This acceleration arises from an extremely weak force on an object due to non-uniform thermal radiation. This force is particularly important for the asteroid Apophis, as it affects the probability of an Earth impact in 2068.

Prior to the detection of Yarkovsky acceleration on Apophis, astronomers had concluded that a potential impact with Earth in 2068 was impossible. The detection of this effect acting on Apophis means that the 2068 impact scenario is still a possibility.


Apophis is noteworthy because of its extremely close approach to the Earth on Friday, April 13, 2029, when the 300 meter-sized asteroid will become visible to the unaided eye as it passes within the belt of communications satellites orbiting the Earth.

Quote
... "The new observations we obtained with the Subaru telescope earlier this year were good enough to reveal the Yarkovsky acceleration of Apophis, and they show that the asteroid is drifting away from a purely gravitational orbit by about 170 meters per year, which is enough to keep the 2068 impact scenario in play."

... Further observations to refine the amplitude of the Yarkovksy effect and how it affects Apophis' orbit are underway. Astronomers will know well before 2068 if there is any chance of an impact.

https://www.hawaii.edu/news/2020/10/26/new-massive-asteroid-findings/

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kassy

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Re: Astronomical news
« Reply #411 on: October 29, 2020, 03:48:26 PM »
Scientists Find Gas Linked to Life in Atmosphere of Venus
https://www.theguardian.com/science/2020/sep/14/scientists-find-gas-linked-to-life-in-atmosphere-of-venus

Phosphine, released by microbes in oxygen-starved environments, was present in quantities larger than expected
Turns out to be a faulty step in analysis. Paper can be found here:
https://arxiv.org/abs/2010.09761

Re-analysis of the 267-GHz ALMA observations of Venus: No statistically significant detection of phosphine

Conclusions: We find that the published 267-GHz ALMA data provide no statistical evidence for phosphine in the atmosphere of Venus.
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vox_mundi

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Re: Astronomical news
« Reply #412 on: October 29, 2020, 04:15:49 PM »
Saves a trip. 

-------------------------------------------

Where Were Jupiter and Saturn Born?
https://phys.org/news/2020-10-jupiter-saturn-born.html

New work led by Carnegie's Matt Clement reveals the likely original locations of Saturn and Jupiter. These findings refine our understanding of the forces that determined our Solar System's unusual architecture, including the ejection of an additional planet between Saturn and Uranus, ensuring that only small, rocky planets, like Earth, formed inward of Jupiter.

Clement and his co-authors—Carnegie's John Chambers, Sean Raymond of the University of Bordeaux, Nathan Kaib of University of Oklahoma, Rogerio Deienno of the Southwest Research Institute, and André Izidoro of Rice University—conducted 6,000 simulations of our Solar System's evolution, revealing an unexpected detail about Jupiter and Saturn's original relationship.

Jupiter in its infancy was thought to orbit the Sun three times for every two orbits that Saturn completed. But this arrangement is not able to satisfactorily explain the configuration of the giant planets that we see today. The team's models showed that a ratio of two Jupiter orbits to one Saturnian orbit more consistently produced results that look like our familiar planetary architecture.

The model also showed that the positions of Uranus and Neptune were shaped by the mass of the Kuiper belt—an icy region on the Solar System's edges composed of dwarf planets and planetoids of which Pluto is the largest member—and by an ice giant planet (... Planet 9?) that was kicked out in the Solar System's infancy.



Matthew S. Clement et al, Born eccentric: Constraints on Jupiter and Saturn's pre-instability orbits, Icarus (2020)
https://www.sciencedirect.com/science/article/abs/pii/S0019103520304644
« Last Edit: October 29, 2020, 06:29:20 PM by vox_mundi »
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vox_mundi

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Re: Astronomical news
« Reply #413 on: October 29, 2020, 09:43:53 PM »
About Half of Sun-Like Stars Could Host Rocky, Potentially Habitable Planets
https://www.nasa.gov/feature/ames/kepler-occurrence-rate



According to new research using data from NASA’s retired planet-hunting mission, the Kepler space telescope, about half the stars similar in temperature to our Sun could have a rocky planet capable of supporting liquid water on its surface.

Our galaxy holds an estimated 300 million of these potentially habitable worlds, based on results in a study released today and to be published in The Astronomical Journal. Some of these exoplanets could even be our interstellar neighbors, with four potentially within 30 light-years of our Sun and the closest likely to be about 20 light-years from us.

"Kepler already told us there were billions of planets, but now we know a good chunk of those planets might be rocky and habitable," said the lead author Steve Bryson, a researcher at NASA's Ames Research Center in California's Silicon Valley. "Though this result is far from a final value, and water on a planet's surface is only one of many factors to support life, it's extremely exciting that we calculated these worlds are this common with such high confidence and precision."

Steve Bryson et al, The Occurrence of Rocky Habitable Zone Planets Around Solar-Like Stars from Kepler Data, The Astronomical Journal, arXiv:2010.14812v1,
https://arxiv.org/abs/2010.14812

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Sigmetnow

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Re: Astronomical news
« Reply #414 on: October 31, 2020, 08:35:54 PM »
—- OSIRIS-REx: Bennu asteroid bits now sealed inside
Quote
NASA's OSIRIS-REx (@OSIRISREx) 10/29/20, 4:19 PM
 
I’ve officially closed the Sample Return Capsule! The sample of Bennu is sealed inside and ready for our voyage back to Earth. The SRC will touch down in the Utah desert on Sep. 24, 2023. Thanks, everyone, for being a part of my journey #ToBennuAndBack 
➡️ https://twitter.com/osirisrex/status/1321909550547652619
11 sec: closing the lid.

“In order to properly prepare for protecting the sample returned from Bennu while also studying it, ARES will also have new cleaning facilities, tools and storage areas in addition to the new labs in development. This will allow scientists to study Bennu's surface material without damaging it.
The ARES team has been planning for this return for more than 15 years. …”

NASA spacecraft safely seals up asteroid sample to return to Earth
https://www.cnn.com/2020/10/29/world/nasa-asteroid-bennu-sample-stow-scn-trnd/index.html
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vox_mundi

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Re: Astronomical news
« Reply #415 on: November 09, 2020, 10:23:24 PM »
Second Cable Fails at Arecibo, Causing Even More Damage to Famed SETI Dish
https://gizmodo.com/second-cable-fails-at-arecibo-causing-even-more-damage-1845619120/amp

Another cable has fallen onto the reflector dish at the Arecibo Observatory in Puerto Rico, in yet another frustrating setback for this beloved facility.

The main support cable of the Arecibo Observatory failed and fell onto the dish below at 7:30 p.m. Puerto Rico time on Friday November 6, reports UCF Today. The extent of the damage is not yet known, but the dish was damaged further, as were some nearby cables. No one was hurt, but a safety zone has been set up around the facility as a precaution. With two failed support cables in three months, it’s imperative that response teams now find a way to stabilize the structure.

The first incident happened on August 10, when a 3-inch-thick auxiliary cable fell onto the observatory’s main reflector dish, creating a 10-foot-long gash. The reason for the failure has yet to be determined, but the auxiliary cable appears to have slipped out from its socket. This doesn’t appear to be the case for the main cable, which simply snapped, possibly a result of the extra weight imposed on the remaining cables, according to observatory officials. As UCF Today reports, officials were aware of broken wires on the main cable, and engineers were scheduled to make emergency repairs this week.

Like the failed auxiliary cable, the main cable connects to the main support tower. The incident from this past August also resulted in damage to the Gregorian Dome and the platform used to access the dome. The facility at Arecibo is managed by the University of Central Florida on behalf of the U.S. National Science Foundation, under a cooperative agreement with Universidad Ana G. Méndez and Yang Enterprises

Progress at Arecibo has been slow since the August incident, as officials struggle to pinpoint the cause of the auxiliary cable failure. The failed socket, for example, was sent to NASA for a forensic analysis. Arecibo officials had previously asked the National Science Foundation for funds needed to make temporary repairs, but the projected cost of the repairs is not yet known. The observatory, which was built in the 1960s, has a long history of fiscal uncertainty, in addition to enduring damage from hurricanes and earthquakes.

... asking the NSF for money while Trump is in office is a waste of time.

https://www.ucf.edu/news/a-second-cable-fails-at-nsfs-arecibo-observatory-in-puerto-rico/

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morganism

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Re: Astronomical news
« Reply #416 on: November 09, 2020, 10:41:19 PM »
That ice sheet on Mars thing above, was postulated by Gold in the Deep Hot Biosphere book.

He pointed out the river beds to nowhere, and said that the sides of the shield volcanoes were unstable unless supported by ice sheets. Those shield volcanoes have steep walled cliffs for the bottom halves. The landing site for Curiosity shows the same geo, tall, unsupported sedimentary structures, that argue for mud volcanoes up thru an ice sheet.

I have argued with some others about the amount of meteroites sitting on the surface of Mars, with no craters associated with them. With nearly no atmo, they should have hit at between 3 and 13 kps, doing significant damage.
If they fell on the ice sheet , they would end up as our scattered glacial boulders are.


vox_mundi

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Re: Astronomical news
« Reply #417 on: November 09, 2020, 10:58:25 PM »
Interesting hypothesis, Thanks.
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vox_mundi

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Re: Astronomical news
« Reply #418 on: November 10, 2020, 08:48:03 PM »
Perseverance Rover is 100 Days Out
https://phys.org/news/2020-11-perseverance-rover-days.html

8,640,000 seconds to go before Perseverance touches down on the Red Planet, becoming history's next Mars car.

“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

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vox_mundi

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Re: Astronomical news
« Reply #419 on: November 11, 2020, 09:42:43 PM »
Tree Rings May Hold Clues to Impacts of Distant Supernovas On Earth
https://phys.org/news/2020-11-tree-clues-impacts-distant-supernovas.html

Massive supernova explosions happening thousands of light-years from Earth may have left traces in our planet's biology and geology, according to new research by University of Colorado Boulder geoscientist Robert Brakenridge. The study is published this month in the International Journal of Astrobiology

... A very nearby supernova could be capable of wiping human civilization off the face of the Earth. But even from farther away, these explosions may still take a toll, Brakenridge said, bathing our planet in dangerous radiation and damaging its protective ozone layer.

To study those possible impacts, Brakenridge searched through the planet's tree ring records for the fingerprints of these distant, cosmic explosions. His findings suggest that relatively close supernovas could theoretically have triggered at least four disruptions to Earth's climate over the last 40,000 years.

"These are extreme events, and their potential effects seem to match tree ring records," Brakenridge said.

His research hinges on carbon-14, a carbon isotope that occurs only in tiny amounts on Earth. Radiocarbon is formed when cosmic rays from space bombard our planet's atmosphere on an almost constant basis. Nearby supernova could significantly increase its occurrence.

Scientists have discovered a handful of cases in which the concentration of this isotope inside tree rings spikes—suddenly and for no apparent earthly reason. Many scientists have hypothesized that these several-year-long spikes could be due to solar flares or huge ejections of energy from the surface of the sun.

"We're seeing terrestrial events that are begging for an explanation," Brakenridge said. "There are really only two possibilities: A solar flare or a supernova. I think the supernova hypothesis has been dismissed too quickly."

To test the hypothesis, Brakenridge turned to the past. He assembled a list of supernovas that occurred relatively close to Earth over the last 40,000 years. Scientists can study these events by observing the nebulas they left behind. He then compared the estimated ages of those supernova to the tree ring record on the ground.

He found that of the eight closest supernovas studied, all seemed to be associated with unexplained spikes in the radiocarbon record on Earth. He considers four of these to be especially promising candidates. Take the case of a former star in the Vela constellation. This celestial body, which once sat about 815 lightyears from Earth, went supernova roughly 13,000 years ago. Not long after that, radiocarbon levels jumped up by nearly 3% on Earth—a staggering increase.

Scientists still have trouble dating past supernovas, making the timing of the Vela explosion uncertain with a possible error of as much as 1,500 years.

Some astronomers think they've picked up signs that Betelgeuse, a red giant star in the constellation Orion, might be on the verge of collapsing and going supernova. And it's only 642.5 light-years from Earth, much closer than Vela.

"We can hope that's not what's about to happen because Betelgeuse is really close," he said said.

G. Robert Brakenridge, Solar system exposure to supernova γ radiation, International Journal of Astrobiology (2020).
https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/solar-system-exposure-to-supernova-radiation/93A83A960E20D33182A720A08D13F40C
« Last Edit: November 13, 2020, 02:41:22 AM by vox_mundi »
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vox_mundi

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Re: Astronomical news
« Reply #420 on: November 13, 2020, 02:43:26 AM »
Arecibo Radio Telescope Observatory In Puerto Rico Is at Risk of Collapsing
https://api.nationalgeographic.com/distribution/public/amp/science/2020/11/arecibo-observatory-in-puerto-rico-at-risk-of-collapsing



One of the world’s most venerable radio telescopes is on the brink of catastrophe, triggering a frantic race by engineers at the Arecibo Observatory in Puerto Rico to save it after two critical cables supporting a 900-ton equipment platform broke.

The platform, held aloft over a massive dish by cables strung to towers, must be quickly stabilized, or it could crash to the ground and destroy the telescope. With the loss of these two cables, the remaining cables are under increased strain, and it’s uncertain whether rescue efforts will be successful.

Suspended from three towers, the telescope’s platform hovers some 500 feet above the thousand-foot-wide dish. In August, an auxiliary cable slipped from its socketand plummeted into the dish, carving a 100-foot-long gash into its reflective panels. Before crews could repair that cable, another one attached to the same tower rupturedon November 6. This second broken cable is one of four primary ones connecting that tower to the platform.

Each of the observatory’s towers has four primary cables, but only two are required to keep the platform aloft—assuming they’re in decent shape. Tower four (named because it’s at the four o’clock position if noon is north) is now down to just three primaries. If another one of those cables fails, it’s unclear whether two aging cables will be able to hold the platform.

“It’s an ugly situation for sure,” says Frank Drake, a former Arecibo director. “When you have cables breaking like that, it could precipitate at any moment a chain reaction with more cables breaking, and the whole thing falling down.”

Although it might look small relative to the dish, the suspended structure is truly massive—a small house could easily fit inside the dome housing the reflector system.

The platform is held up by 18 thick, steel cables strapped to three concrete towers, the tallest of which measures 365 feet. In addition to the four primary cables on each tower, two auxiliaries per tower were installed in the 1990s to help stabilize the structure and bear additional weight.

If tower four fails, the platform could either crash through the dish or make a pendulous swing into a nearby cliff. Without the platform’s weight keeping the towers balanced, it’s possible all three could topple into the surrounding jungle.



------------------------------------------------

« Last Edit: November 13, 2020, 02:55:04 AM by vox_mundi »
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Tom_Mazanec

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Re: Astronomical news
« Reply #421 on: November 14, 2020, 04:07:25 PM »
Another Rare Earth factor: You need just the right amount of uranium and thorium to have a geomagnetic field protecting your atmosphere for geologically long timescales:

Radiogenic Heating and Its Influence on Rocky Planet Dynamos and Habitability
https://iopscience.iop.org/article/10.3847/2041-8213/abc251
Quote
Abstract
The thermal evolution of rocky planets on geological timescales (Gyr) depends on the heat input from the long-lived radiogenic elements potassium, thorium, and uranium. Concentrations of the latter two in rocky planet mantles are likely to vary by up to an order of magnitude between different planetary systems because Th and U, like other heavy r-process elements, are produced by rare stellar processes. Here we discuss the effects of these variations on the thermal evolution of an Earth-size planet, using a 1D parameterized convection model. Assuming Th and U abundances consistent with geochemical models of the Bulk Silicate Earth based on chondritic meteorites, we find that Earth had just enough radiogenic heating to maintain a persistent dynamo. According to this model, Earth-like planets of stars with higher abundances of heavy r-process elements, indicated by the relative abundance of europium in their spectra, are likely to have lacked a dynamo for a significant fraction of their lifetimes, with potentially negative consequences for hosting a biosphere. Because the qualitative outcomes of our 1D model are strongly dependent on the treatment of viscosity, further investigations using fully 3D convection models are desirable.
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kassy

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Re: Astronomical news
« Reply #422 on: November 14, 2020, 05:31:51 PM »
It is basically another input into the goldilocks equation for planets and since suns and their planetary discs are more or less made from the same material you can get some info on the make up by looking at the starts spectrum.
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Re: Astronomical news
« Reply #423 on: November 16, 2020, 07:52:42 PM »
At least AGW won't get the Earth this hot!

The Most Hellish Planet Yet
https://www.airspacemag.com/daily-planet/most-hellish-planet-yet-180976295/
Quote
In general, K stars are suitable for hosting life-bearing worlds, and some are even thought to have “superhabitable” worlds in orbit around them. K2-141b is quite the opposite. With an estimated mass about five times that of Earth, it orbits its star more than 100 times closer than Earth orbits the Sun, making its year less than seven hours long! Temperatures near the surface are so high that the planet likely has a magma ocean tens of kilometers deep.
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vox_mundi

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Re: Astronomical news
« Reply #424 on: November 18, 2020, 10:57:00 PM »
Mystery of Glowing Cosmic 'Eye' Finally Solved
https://gizmodo.com/mystery-of-glowing-cosmic-eye-finally-solved-1845706044/amp



Thousands of years ago, a small star was orbiting a larger star with roughly the same mass as our Sun. As the larger star got older, however, it became bloated, expanding to reach very close to its smaller companion. The smaller star—around one-tenth the size of our Sun—fell into a downward spiral that produced a gaseous disk. The big star eventually subsumed the smaller star, producing an expanding cloud of debris that was sliced in half by the disk. This merger resulted in the two cone-shaped debris clouds we see today.

In the thousands of years that followed, the expanding cloud of debris cooled, forming hydrogen molecules that interacted with the stellar medium. Today, we see these collisions as bright ultraviolet emissions. The cloud is now “dissolving into the interstellar medium,” and “we’re just happening to catch it as all the exciting particles are present,” Hoadley told reporters.

Hoadley expects the Blue Ring Nebula to last for another thousand to a few tens of thousands of years, after which time the feature will disappear completely. It’s a veritable blink of the eye in cosmological terms, and a wonderful opportunity to do some fascinating science



https://arstechnica.com/science/2020/11/when-stars-collide-solving-the-16-year-mystery-of-the-blue-ring-nebula/
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vox_mundi

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Re: Astronomical news
« Reply #425 on: November 18, 2020, 11:00:02 PM »
A small asteroid came closer to Earth than even SpaceX Starlink satellites
https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2020%20VT4

An asteroid set a new mark on Friday for the closest pass by our planet without actually impacting.

The space rock was discovered with the Asteroid Terrestrial-impact Last Alert System, or ATLAS, run by NASA and the University of Hawaii. It has been designated 2020 VT4, and it came within just 240 miles (386 kilometers) of Earth's surface on Friday. That's closer even than objects in low-earth orbit including the International Space Station and SpaceX's Starlink broadband constellation.

https://fallingstar.com/home.php
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Sigmetnow

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Re: Astronomical news
« Reply #426 on: November 19, 2020, 07:20:42 PM »
Quote
National Science Foundation (@NSF)11/19/20, 11:32 AM
Following engineering assessments concluding damage to Arecibo Observatory cannot be addressed without endangering the lives and safety of crew and staff, NSF plans to decommission the 305-meter telescope

NSF’s first priority is safety. Multiple assessments by independent engineering companies found the telescope structure is in danger of a catastrophic failure and its cables may no longer be capable of carrying the loads they were designed to support. 
https://twitter.com/nsf/status/1329462672627277829

NSF begins planning for decommissioning of Arecibo Observatory’s 305-meter telescope due to safety concerns
https://www.nsf.gov/news/news_summ.jsp?cntn_id=301674
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vox_mundi

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Re: Astronomical news
« Reply #427 on: November 19, 2020, 07:49:02 PM »
900-Ton Platform Threatens to Crush Famed Arecibo Observatory Dish
https://gizmodo.com/900-ton-platform-threatens-to-crush-famed-arecibo-obser-1845687462



The Arecibo Observatory in Puerto Rico is in an exceptionally precarious state following the recent failure of two support cables, placing the future of this renowned facility in doubt.

With two support cables gone, the 900-ton platform located directly above the dish is now being supported by the remaining main and auxiliary cables—some of which are already fraying, according to the University of Central Florida (UCF).

https://www.ucf.edu/news/ucf-delivers-engineering-options-for-arecibo-observatory-ao/

Preliminary analysis indicates the main cable, which failed on Nov. 6, should have easily handled the extra load based on design capacity. Engineers suspect it is likely that the second cable failed because it has degraded over time and has been carrying extra load since August. A final determination could not be made without retrieving and analyzing the second cable.

The engineering firms cannot verify the integrity of the other cables at this time supporting the 900-ton platform. Each of the structure’s remaining cables is now supporting more weight than before, increasing the likelihood of another cable failure, which would likely result in the collapse of the entire structure.

Other wire breaks on two of the remaining main cables have also been observed. The situation is dynamic and poses a serious safety risk to employees and contractors.

“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

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kassy

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Re: Astronomical news
« Reply #428 on: November 19, 2020, 07:53:34 PM »
Where are the Thunderbirds when you need them?  :(
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Re: Astronomical news
« Reply #429 on: November 19, 2020, 11:46:41 PM »
Fortunately the Chinese have Tianyan to take over.
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Sigmetnow

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Re: Astronomical news
« Reply #430 on: November 20, 2020, 06:01:48 PM »
Arecibo Observatory faces demolition after cable failures – Spaceflight Now
Quote
An engineering firm hired by the University of Central Florida to assess the structure concluded it would be unsafe to proceed with repairs. Even stress tests to determine the strength of the remaining cables could trigger a catastrophic collapse.

Instead, engineers recommended a controlled demolition, bringing down the suspended instrument platform in a way that will prevent damage to other structures at the periphery of the dish by making sure the towers themselves don’t collapse and by ensuring no cables whip into those structures.

“The telescope is at serious risk of an unexpected, uncontrolled collapse,” said Ralph Gaume, director of NSF’s Division of Astronomical Sciences. “According to engineering assessment, even attempted stabilization, or testing the table could result in accelerating the catastrophic failure.

“Engineers cannot tell us the safety margin of the structure, but they have advised NSF that the structure will collapse in the near future on its own.”

Plans for bringing down the instrument platform have not yet been finalized and it’s not yet known whether explosives will be used in a controlled demolition or whether it might be possible to somehow lower the platform to the dish below.

However it plays out, the 1,000-foot-wide telescope will essentially be destroyed. While the laser facility and visitor’s center will hopefully be preserved, the radio telescope itself will be no more. ...
https://spaceflightnow.com/2020/11/19/arecibo-observatory-faces-demolition-after-cable-failures/
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Sigmetnow

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Re: Astronomical news
« Reply #431 on: November 20, 2020, 06:17:37 PM »
Boeing subsidiary ready to launch satellite deorbiting experiment
Quote
The DragRacer experiment includes two satellites — built by Millennium Space Systems — that will separate shortly after launching on the Electron rocket in a 310-mile-high (500-kilometer) sun-synchronous orbit. One satellite — named Alchemy — will extend a 230-foot-long (70-meter) electrically conductive tether, a device designed to increase the surface area of the spacecraft, allowing it to succumb to aerodynamic drag and naturally re-enter the atmosphere and burn up.

Both DragRacer spacecraft are identical, except that one carries the tether and the other — named Augury — does not.

According to preflight predictions, the satellite with the tether could re-enter the atmosphere within 45 days. The spacecraft without the tether — the control for the experiment — is expected to remain in orbit for around seven years, according to mission team members.

The device affixed to DragRacer’s Alchemy satellite is called a Terminator Tape. Developed by Tethers Unlimited, the tape measures just a few inches wide, but it can spool out to lengths of hundreds of feet.

The DragRacer experiment is a purely commercial experiment to quantify the effectiveness of the Terminator Tape technology, which Millennium and Tethers Unlimited say is a more reliable, lower cost, and less complex alternative to other deorbit methods, such as drag sails or propulsive thrusters.

“This scientific method experiment will demonstrate Millennium’s ability to field and fly a low-cost and straightforward orbital debris mitigation solution that doesn’t require added mass, volume, cost and complexity of propulsion system to deorbit a satellite in low Earth orbit,” said Stan Dubyn, founder and CEO of Millennium Space Systems, in a press release.

Tethers Unlimited’s Terminator Tape technology has flown before. The company says the tether module — which attaches on the exterior of a host spacecraft — weighs about 2 pounds and is about the size of a notebook, and is suitable for a range of satellite sizes. ...
https://spaceflightnow.com/2020/11/19/boeing-subsidiary-ready-to-launch-satellite-deorbiting-experiment/
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oren

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Re: Astronomical news
« Reply #432 on: November 20, 2020, 09:07:21 PM »
Nice idea, to solve a problem that is becoming bigger.

vox_mundi

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Re: Astronomical news
« Reply #433 on: November 20, 2020, 09:28:01 PM »
Field Geology at Mars' Equator Points to Ancient Megaflood
https://phys.org/news/2020-11-field-geology-mars-equator-ancient.html

Floods of unimaginable magnitude once washed through Gale Crater on Mars' equator around 4 billion years ago—a finding that hints at the possibility that life may have existed there, according to data collected by NASA's Curiosity rover and analyzed in joint project by scientists from Jackson State University, Cornell University, the Jet Propulsion Laboratory and the University of Hawaii.

The research, "Deposits from Giant Floods in Gale Crater and Their Implications for the Climate of Early Mars," was published Nov. 5 in Scientific Reports.

The raging megaflood—likely touched off by the heat of a meteoritic impact, which unleashed ice stored on the Martian surface—set up gigantic ripples that are tell-tale geologic structures familiar to scientists on Earth.

This case includes the occurrence of giant wave-shaped features in sedimentary layers of Gale crater, often called "megaripples" or antidunes that are about 30-feet high and spaced about 450 feet apart, according to lead author Ezat Heydari, a professor of physics at Jackson State University.

The antidunes are indicative of flowing megafloods at the bottom of Mars' Gale Crater about 4 billion years ago, which are identical to the features formed by melting ice on Earth about 2 million years ago, Heydari said.

The most likely cause of the Mars flooding was the melting of ice from heat generated by a large impact, which released carbon dioxide and methane from the planet's frozen reservoirs. The water vapor and release of gases combined to produce a short period of warm and wet conditions on the red planet.

Condensation formed water vapor clouds, which in turn created torrential rain, possibly planetwide. That water entered Gale Crater, then combined with water coming down from Mount Sharp (in Gale Crater) to produce gigantic flash floods that deposited the gravel ridges in the Hummocky Plains Unit and the ridge-and-trough band formations in the Striated Unit.

The Curiosity rover science team has already established that Gale Crater once had persistent lakes and streams in the ancient past. These long-lived bodies of water are good indicators that the crater, as well as Mount Sharp within it, were capable of supporting microbial life.

"Early Mars was an extremely active planet from a geological point of view," Fairén said. "The planet had the conditions needed to support the presence of liquid water on the surface—and on Earth, where there's water, there's life.

"So early Mars was a habitable planet," he said. "Was it inhabited? That's a question that the next rover Perseverance ... will help to answer."



E. Heydari et al, Deposits from giant floods in Gale crater and their implications for the climate of early Mars, Scientific Reports (2020)
https://www.nature.com/articles/s41598-020-75665-7
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Sigmetnow

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Re: Astronomical news
« Reply #434 on: November 21, 2020, 03:12:12 AM »
Get ready for the 'Great Conjunction' of Jupiter and Saturn
The "Great Conjunction" on Dec. 21, 2020 will be a once-in-a-lifetime opportunity to see Jupiter and Saturn together through a telescope.
Quote
All through the summer and into the fall, the two gas giants of the solar system, Jupiter and Saturn, have been calling attention to themselves in the southern evening sky.

Jupiter of course, always appears brilliant and is usually one of the brightest nighttime objects, but in recent months it has stood out even more than usual because of the presence of bright Saturn trailing just off to its left (east).

Appearing about one-twelfth as bright, Saturn has, in a way, served as Jupiter's "lieutenant" in this year of 2020. ...   
https://www.space.com/jupiter-saturn-great-conjunction-2020
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vox_mundi

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Re: Astronomical news
« Reply #435 on: November 23, 2020, 05:22:16 PM »
Scientists Have Re-analyzed Their Data and Still See a Signal of Phosphine at Venus—Just Less of It
https://phys.org/news/2020-11-scientists-re-analyzed-phosphine-venusjust.html

In September, an international team announced that they had discovered phosphine gas (PH3) in the atmosphere of Venus based on data obtained by the Atacama Millimeter-submillimeter Array (ALMA) in Chile and the James Clerk Maxwell Telescope (JCMT) in Hawaii. The news was met with its fair share of skepticism and controversy since phosphine is considered a possible indication of life (AKA a biosignature).

Shortly thereafter, a series of papers was published that questioned the observations and conclusions, with one team going as far as to say there was "no phosphine" in Venus's atmosphere at all. Luckily, after re-analyzing the ALMA data, the team responsible for the original discovery concluded that there is indeed phosphine in the cloud tops of Venus—just not as much as they initially thought.

In the original study, which was published in the Sept. 14th issue of Nature Astronomy, the team presented findings from ALMA and the JCMT that indicated the presence of PH3 around Venus' cloud deck. On Earth, phosphine is part of the phosphorus biochemical cycle and is likely the result of phosphate reduction in decaying organic matter. On Venus, there are no known chemistry or photochemical pathways for its creation.

... In one study, which was led by researchers from NASA Goddard and appeared in a Nature Astronomy article (Oct. 26, 2020), also cast doubt on the analysis and interpretation of the ALMA and JCMT datasets. Here, the research team indicated that the spectral data that was interpreted as phosphine (PH3) was actually too close to sulfur dioxide (SO2), which is common in Venus atmosphere.

According to another study that was led by Leiden University (November 17, 2020, Astronomy & Astrophysics), the spectral data obtained by ALMA could be explained by the presence of compounds other than phosphine gas. From this, they concluded that there "no statistically significant detection of phosphine" in Venus' atmosphere and that the previous results were, in fact, "spurious."

Jane Greaves, who led the discovery team (and is an astronomer at Cardiff University, U.K.), claims that they were motivated to reexamine their original conclusions because the original ALMA data contained a "spurious signal" that could have thrown off their results. When the corrected ALMA data was posted on November 16th, Greaves and her colleagues ran a fresh analysis and posted it ahead of peer review on arXiv.

According to Greaves and her colleagues, the ALMA data demonstrated a spectral signature that cannot be explained by anything other than the compound phosphene. This, they claim, is further bolstered by the JCMT spectra that indicated the chemical fingerprints of phosphine. Based on the new ALMA data, the team estimates that phosphine levels average at about 1 ppb—about one-seventh of their earlier estimate.

These levels, they indicate, likely peak at five parts per billion (ppm) and vary over time and depending on location.
If true, this situation is similar to what scientists have observed on Mars, where methane levels wax and wane over the course of a Martian year and vary from place to place.

Inspired by the possibility, biochemist Rakesh Mogul of the California State Polytechnic University in Pomona and his colleagues reexamined data from NASA's Pioneer Venus mission. In 1978, this missions studies Venus' cloud layer using a probe that it dropped into the atmosphere. Based on their reanalysis of the data, Mogul and his colleagues found evidence of phosphorus.

This could evidence of phosphine or some other phosphorus compound, though Mogul and his team believe phosphine is the most likely candidate. Regardless, several scientists argued at VEXAG that a modest level of even 1 ppm phosphine cannot be attributed to processes like volcanism or lightning. There was also the recent announcement that the amino acid glycine was discovered in Venus's atmosphere, another potential biomarker.

Alexandra Witze. Prospects for life on Venus fade—but aren't dead yet, Nature (2020)
https://www.nature.com/articles/d41586-020-03258-5
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Sigmetnow

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Re: Astronomical news
« Reply #436 on: November 23, 2020, 06:28:00 PM »
Spacecraft With Precious Asteroid Cargo Is Almost Home After 5-Billion Km Trek
Quote
In the dusty desert town of Woomera, in the South Australian desert, scientists are getting ready. On 6 December 2020, after six years in space, the Japan Aerospace Exploration Agency's Hayabusa2 spacecraft will finally return to Earth.

It carries with it a cargo unbelievably rare, precious, and hard-won - at least 100 milligrams of material collected from the surface of asteroid Ryugu. It will drop the capsule containing the sample to Earth, the spacecraft itself continuing on to visit more asteroid targets.

Hayabusa2's return will mark a milestone in a remarkable feat of space science, a total journey of around 5.24 billion kilometres (almost 3.3 billion miles). Asteroid Ryugu - formerly known as 1999 JU3 - is on an elliptical orbit that carries it just inside Earth's orbital path around the Sun, and out almost as far as Mars' orbit.
...
Meanwhile, Hayabusa2's flight will continue. Its next stop will be asteroid (98943) 2001 CC21 in July 2026, after which it will continue on to asteroid 1998 KY26 for a July 2031 rendezvous.
https://www.sciencealert.com/hayabusa2-is-about-to-return-to-earth-bringing-us-a-piece-of-precious-asteroid
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Sigmetnow

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Re: Astronomical news
« Reply #437 on: November 23, 2020, 06:42:58 PM »
China prepping for mission to bring back material from moon
Chinese technicians are making final preparations for a mission to bring back material from the moon’s surface for the first time in nearly half a century
Quote
WENCHANG, China -- Chinese technicians were making final preparations Monday for a mission to bring back material from the moon's surface for the first time in nearly half a century — an undertaking that could boost human understanding of the moon and of the solar system more generally.

Chang’e 5 — named for the Chinese moon goddess — is the country's most ambitious lunar mission yet. If successful, it would be a major advance for China's space program, and some experts say it could pave the way for bringing samples back from Mars or even a crewed lunar mission.

The four modules of the Chang’e 5 spacecraft are expected be sent into space Tuesday aboard a massive Long March-5 rocket from the Wenchang launch center along the coast of the southern island province of Hainan, according to a NASA description of the mission.

The secretive Chinese National Space Administration has only said that a launch is scheduled for late November, although the Lunar Exploration Project said in a statement Monday that success in orbiting, descending and returning would “lay a solid foundation for future missions.”

The mission's key task is to drill 2 meters (almost 7 feet) beneath the moon's surface and scoop up about 2 kilograms (4.4 pounds) of rocks and other debris to be brought back to Earth, according to NASA. That would offer the first opportunity to scientists to study newly obtained lunar material since the American and Russian missions of the 1960s and 1970s.

After making the three-day trip from Earth, the Chang’e 5 lander’s time on the moon is scheduled to be short and sweet. It can only stay one lunar daytime, or about 14 Earth days, because it lacks the radioisotope heating units to withstand the moon’s freezing nights.

The lander will dig for materials with its drill and robotic arm and transfer them to what's called an ascender, which will lift off from the moon and dock with the “service capsule.” The materials will then be moved to the return capsule for the trip home to Earth. ...
https://abcnews.go.com/Technology/wireStory/china-final-preparations-latest-lunar-mission-74353397
People who say it cannot be done should not interrupt those who are doing it.