HiPOD (30 September 2018): Lovely Sleekness
– This crescent-shaped dune (called a “barchan dune”) is located within a crater that is to the east of Toro Crater. (280 km above the surface, less than 1 km across)
NASA/JPL/University of Arizona
Космический трэк пространственных событий Тайны Мира, НЛО пришельцы, наука, космос, древние, мегалиты, археология. Secrets, unknown, UFO aliens, science, space, ancient civilizations, megaliths, archeology
– This crescent-shaped dune (called a “barchan dune”) is located within a crater that is to the east of Toro Crater. (280 km above the surface, less than 1 km across)
NASA/JPL/University of Arizona
In this Context Camera image in Terra Cimmeria, we see a 30-kilometer diameter crater, filled-in with materials that created bedrock, and through subsequent erosion, wind-driven particles.
There is a ring of exposed light-toned bedrock at the base of the crater wall. This distinctive ring suggests high winds climbing up the crater wall slope may be responsible for the erosion and the extent of bedrock exposure we see. A close-up on the southeastern part of these deposits shows a mound of bedrock with beautiful color contrasts. The variation in color represents diverse minerals in the rock.
There is also a small degraded crater (about 300-meter diameter) to the left of the exposed bedrock. Fine-grained materials trapped inside the crater appear as wind-driven ripples or small dune-forms.
NASA/JPL/University of Arizona
The ultimate origin of the sediment that forms Martian dunes has long been debated. While sand dunes on Earth are primarily sourced by quartz-bearing components of granitic continental crust, it’s often suggested that sand on Mars derives from eroded volcanic flows or sedimentary deposits, but exact sources are often vague.
This image reveals a unique situation where this small dune field occurs along the summit of the large 1-mile-tall mound near the center of Juventae Chasma. The layered mound slopes are far too steep for dunes to climb, and bedform sand is unlikely to come from purely airborne material. Instead, the mound’s summit displays several dark-toned, mantled deposits that are adjacent to the dunes and appear to be eroding into fans of sandy material.
NASA/JPL/University of Arizona
Large craters, like this 50-kilometer diameter one, can uplift material from below and form a mountain-like central peak. Craters of this size on Mars become unstable as they form and collapse due to gravity. Craters with central peaks and terraced rims are referred to as “complex” craters.
Geologists study these central peaks because the uplifted bedrock was once deep within the Martian crust. A 3D perspective shows heavily-fractured bedrock exposed within the peak, and also dark-toned and fragmental rocks that formed during the impact process.
Sometimes, we observe similar rocks in the crater wall terraces. Some areas of the terrace show dark-toned materials coating and surrounding the white- and green-colored bedrock. This dark-toned rock was the once-molten material that was produced by the tremendous energy generated during the formation of the crater. Similarly, the impact melt material coats and surrounds the higher-standing bedrock of the peak. There are additional exposures of bedrock in the northern wall-terraces of the crater.
NASA/JPL/University of Arizona
This color-infrared image shows sand dunes in Melas Chasma, located within the Valles Marineris canyon system. The dark-blue and purple colors indicate coarse-grained sands that are comprised of basalt, an iron and magnesium-rich volcanic rock that formed from cooled lava millions of years ago when volcanism was an active process on Mars.
Migrating sand dunes often lead to the erosion and excavation of underlying material; regions where there are active dune fields are ideal places to search for exposed bedrock. Repeated imaging of dunes may also show changes that provide evidence for active surface processes related to wind patterns and climate.
NASA/JPL/University of Arizona
– A Context Camera image shows a small bench in the middle of the Cerberus Fossae at the head of Athabasca Valles. Small cataracts appear on this bench. Do these reflect erosion as water drained back into the subsurface at the conclusion of the flood? (279 km above the surface. Black and white is less than 5 km across; enhanced color is less than 1 km).
NASA/JPL/University of Arizona
– You can also see a crater exit breach in the lower-middle-right. Was a result of overflow from the crater? HiRISE was requested to measure depth of exit breach and depth/width of associated flood channels: was this a single catastrophic flood or seasonally repeating flow? (334 km above the surface, less than 5 km across)
NASA/JPL/University of Arizona
– This image was a request for the now canceled-Red Dragon landing on Mars. (300 km above the surface, less than 5 km across.)
NASA/JPL/University of Arizona
– These dark fans are exposed on the lighter-toned surface due to sublimation, and are blown around by the wind. (322 km above the surface. Black and white is less than 5 km across; enhanced color is less than 1 km.)
NASA/JPL/University of Arizona
Alongside protein-coding genes, the human genome contains many non-coding sequences, so-called ’junk DNA’, including an estimated 8% of our DNA derived from retroviruses. These viruses replicate by inserting their DNA into their hosts’ genomes; if inserted into the DNA of germ cells, giving rise to ovules and sperm, they can be passed on to future generations, eventually losing their viral function. Retroviral insertions in our genome are very ancient, but a more recent, ongoing invasion has been discovered in koalas (pictured), allowing us to study this process in action. Research shows that shuffling genetic material during DNA replication, between koala retrovirus (KoRV) and more ancient retroviral elements in the genome, can quickly disable KoRV. Known as recombination, this mechanism is likely to be a key early step towards retroviral integration. As researchers continue to monitor koala retroviruses, these beloved Australian icons may help us piece together our own genome’s history.
Written by Emmanuelle Briolat
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The AMS has received over 70 reports so far about of a fireball event seen above Florida on October 6th, 2018 around 10:20pm EDT (October 7th 02:20 Universal Time). The fireball was seen primarily from Florida but was also seen from South Carolina and Georgia.
If you witnessed this event and/or if you have a video or a photo of this event, please
Submit an Official Fireball Report
If you want to learn more about Fireballs: read our Fireball FAQ.
The event has been caught on tape by at least two witnesses that were kind enough to share their videos with the AMS:
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It was the Summer comet: 21P/Giacobini-Zinner became visible with a simple pair of binoculars, as it passed perihelion, in September, and reached +7 magnitude. One month later, the comet is fading, but another astronomical may bring it back to the front scene: Draconid meteor shower, associated to meteoroids released from 21P/Giacobini-Zinner nucleus is going to peak on October 8-9. And even if nothing exceptionnal is predicted, perihelion years are sometimes associated to activity outbursts. Stay alerted for the whole activity period!
In 1998 & 1999, 2005, 2011 & 2012, near the last perihelion dates for 21P/Giacobini-Zinner, Draconid outburst were recorded and observed. During the last return of the comet, a meteor outburst with ZHR reaching 300 was predicted and observed (in 2011). But one year later, in 2012, nothing was expected but another outburst, with similar activity levels, was recorded with radio/radar methods. This is why meteor observers shoudl keep alerted this year, even if nothing is predicted.
The “node crossing”, which corresponds to the “classical” maximum, should be reached between October 8, 23h UT and October 9, 01h UT, with a maximum probability at 00h 10min UT on Oct 9. Regarding the potential activity outbursts, dates and times spreads over a longer period. Considering past outbursts, they could happen this year between October 8, 15h 30min UT (considering 2011 outburst) and October 9, 08h 50min UT (considering 1999 outburst). This is why observers should try to observe and monitor the shower as much as they can, because no one can predict when the outburst is more likely to occur.
Except for a potential slight activity enhancement when the Earth will pass close to a dust trail released in 1953, but which has been disturbed in 1985, when our planet came close to it. Rates are difficult to estimate, but times are quite coherent with the different models. Mikiya Sato predicts a ZHR ranging from 20 to 50 on Oct 9, 00h 14min UT, whereas Jérémie Vaubaillon predicts a ZHR~15 on Oct 8, 23h 31min UT, very close from Mikhail Maslov model, which gives a ZHR ~ 10-15 on Oct 8, 23h 34min UT.
Draconids radiant is located in the head of Draco, and is thus circumpolar for many observing sites in the Northern hemisphere, even if it’s best located during the beginning of the night. Draconids are slow meteors: the meteoroid reentry speed is only 20 km/s. They will appear slow moving, even if they are located far from the horizon and radiant. But this slow apparent speed is a good indicator to disregard all sporadic meteor that would accidentally align with the radiant and false activity rates deduced from observations, especially if they are low.
Good luck and clear skies to all!
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ALMA image of CK Vulpeculae. New research indicates that this hourglass-like object is the result of the collision of a brown dwarf and a white dwarf. Credit: ALMA (ESO/NAOJ/NRAO)/S. P. S. Eyres. Hi-res image
Contact:
Charles Blue,
Public Information Officer
(434) 296-0314;
cblue@nrao.edu
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Comet 12P Between Rosette and Cone Nebulas
Image Credit & Copyright: Fritz Helmut Hemmerich
Explanation: Small bits of this greenish-gray comet are expected to streak across Earth’s atmosphere tonight. Specifically, debris from the eroding nucleus of Comet 21P / Giacobini-Zinner, pictured, causes the annual Draconids meteor shower, which peaks this evening. Draconid meteors are easy to enjoy this year because meteor rates will likely peak soon after sunset with the Moon’s glare nearly absent. Patience may be needed, though, as last month’s passing of 21P near the Earth’s orbit is not expected to increase the Draconids’ normal meteor rate this year of (only) a few meteors per hour. Then again, meteor rates are notoriously hard to predict, and the Draconids were quite impressive in 1933, 1946, and 2011. Featured, Comet 21P gracefully posed between the Rosette (upper left) and Cone (lower right) nebulas two weeks ago before heading back out to near the orbit of Jupiter, to return again in about six and a half years.
∞ Source: apod.nasa.gov/apod/ap181008.html
Thornborough Henge at Sunset, Thornborough, Yorkshire, 7.10.18.
Potentially one of the largest prehistoric sites in the UK, this series of massive henges stretches beyond the naked eye. Photographed here is the middle henge ring in the series of three just as the sun made its slow descent.
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Соединение Юпитера ♃ и Сатурна ♄ 21 декабря 2020 16 : 30 по Гринвичу, 21 декабря 2020 года, состоится условное соединение Юпитера ♃ ...