воскресенье, 7 января 2018 г.

Inconstant Moons: A New Lunar Origin Scenario

A recent snowfall followed by warming temperatures produced a foggy night recently, one in which I was out for my usual walk and noticed a beautiful Moon trying to break through the fog layers. The scene was silvery, almost surreal, the kind of thing my wife would write a poem about. For my part, I was thinking about the effect of the Moon on life, and the theory that a large single moon might have an effect on our planet’s habitability. Perhaps its presence helps to keep Earth’s obliquity within tolerable grounds, allowing for a more stable climate.


But that assumes we’ve had a single moon all along, or at least since the ‘big whack’ the Earth sustained from a Mars-sized protoplanet that may have caused the Moon’s formation. Is it possible the Earth has had more than one moon in its past? It’s an intriguing question, as witness a new paper in Nature Geoscience from researchers at the Technion-Israel Institute of Technology and the Weizmann Institute of Science. The paper suggests the Moon we see today is the last of a series of moons that once orbited the Earth.


“Our model suggests that the ancient Earth once hosted a series of moons, each one formed from a different collision with the proto-Earth,” says co-author Assistant Prof. Perets (Technion). “It’s likely that such moonlets were later ejected, or collided with the Earth or with each other to form bigger moons.”


To explore alternatives to giant impact theories, the researchers have produced simulations of early Earth impacts, varying the values for the impactor’s velocity, mass, angle of impact and the initial rotation of the target. The process that emerges involves multiple impacts that would produce small moons, whose gravitational interactions would eventually cause collisions and mergers, to produce the Moon we see today. Here’s how the paper describes the process:


… we consider a multi-impact hypothesis for the Moon’s formation. In this scenario, the proto-Earth experiences a sequence of collisions by medium- to large-size bodies (0.01–0.1M). Small satellites form from the impact-generated disks and migrate outward controlled by tidal interactions, faster at first, and slower as the body retreats away from the proto-Earth. The slowing migration causes the satellites to enter their mutual Hill radii and eventually coalesce to form the final Moon. In this fashion, the Moon forms as a consequence of a variety of multiple impacts in contrast to a more precisely tuned single impact.


Here’s a graphic from the paper (listed as Figure 1) that shows the process at work:


moon_formation


Image (click to enlarge): a,b, Moon- to Mars-sized bodies impact the proto-Earth (a) forming a debris disk (b). c, Due to tidal interaction, accreted moonlets migrate outward. d,e, Moonlets reach distant orbits before the next collision (d) and the subsequent debris disk generation (e). As the moonlet–proto-Earth distance grows, the tidal acceleration slows and moonlets enter their mutual Hill radii. f, The moonlet interactions can eventually lead to moonlet loss or merger. The timescale between these stages is estimated from previous works.


The Hill radius mentioned above describes the gravitational sphere of influence of an object; in this case, meshing Hill radii can produce interactions that sometimes lead to mergers. The paper notes that in head-on impacts, the rotation of the planet is important because the disk needs angular momentum resulting from the rotation to stay stable. With increased rates of rotation, the angular momentum of the disks increases. Moons like ours emerge from many of the simulations:


We find that debris disks resulting from medium- to large-size impactors (0.01–0.1M) have sufficient angular momentum and mass to accrete a sub-lunar-size moonlet. We performed 1,000 Monte Carlo simulations of sequences of N = 10, 20 and 30 impacts each, to estimate the ability of multiple impacts to produce a Moon-like satellite. The impact parameters were drawn from distributions previously found in terrestrial formation dynamical studies. With perfect accretionary mergers, approximately half the simulations result in a moon mass that grows to its present value after ~20 impacts.


If the multi-moon hypothesis proves credible, how would it affect the larger astrobiology question? In Ward and Brownlee’s Rare Earth (Copernicus, 2000), after a discussion of obliquity and the Moon’s effect on the Earth’s early history, the authors say this:


If the Earth’s formation could be replayed 100 times, how many times would it have such a large moon? If the great impactor had resulted in a retrograde orbit, it would have decayed. It has been suggested that this may have happened for Venus and may explain that planet’s slow rotation and lack of any moon. If the great impact had occurred at a later stage in Earth’s formation, the higher mass and gravity of the planet would not have allowed enough mass to be ejected to form a large moon. If the impact had occurred earlier, much of the debris would have been lost to space, and the resulting moon would have been too small to stabilize the obliquity of Earth’s spin axis. If the giant impact had not occurred at all, the Earth might have retained a much higher inventory of water, carbon and nitrogen, perhaps leading to a Runaway Greenhouse atmosphere.


The idea of a series of impacts eventually leading to a larger moon significantly muddies the waters here. It is true that in our Solar System, the inner planets are nearly devoid of moons, but we have no way of extending this situation to exoplanets without collecting the necessary data, which will begin with our first exomoon detections. Certainly if numerous collisions in an early planetary system can produce a large moon, as this paper argues, then we can expect similar collisional scenarios in many systems, making such moons a frequent outcome.


The paper is Rufu, Oharonson & Perets, “A Multiple Impact Hypothesis for Moon Formation,” published online by Nature Geoscience 9 January 2017 (abstract).


tzf_img_post



Source Centauri Dreams Imagining and Planning Interstellar Exploration


qpAdm tour of Europe: Mesolithic to Neolithic transition

For a while now I’ve been trying to work out a way to model present-day Europeans with qpAdm as a mixture of Neolithic and Mesolithic populations. It hasn’t been easy, because often what works for some Europeans doesn’t work for others. But I’ve finally figured it out. The trick is to account for Siberian, East Asian and Sub-Saharan ancestry, by including the Nganasan from Siberia, Onge from the Andaman Islands, and Yoruba from West Africa, respectively, as reference pops. Below is the spreadsheet with the results and outgroups. Judging by the chisq and tail prob, most of the fits aren’t spectacular, but as far as I can tell, they work. Moreover, in the entire analysis not a single standard error reached 2%. Based on my experience with qpAdm, that’s a remarkable thing for such a complex analysis, and I think it suggests that the reference populations are relevant. Interestingly, while, as expected, the Nganasan-related admixture peaks in far Northern Europe, the Onge-related ancestry is, perhaps surprisingly, most pronounced in Southern Europe. Any ideas why? My thoughts on that here.



Update 014/01/2017: If you guys want to reproduce my analysis, but you don’t have the same dataset, which is more than likely, you should be able to get very similar results using the full Human Origins dataset. Try these reference pops and outgroups.


pleft

Barcin_Neolithic

Caucasus_HG (Kotias)

Eastern_HG (Karelia_HG x2, Samara_HG)

Nganasan

Onge

Western_HG (Hungary_HG, Iberia_HG, Loschbour)

Yoruba (from the HGDP) pright

AG3-MA1

Chukchi

Han

Karitiana

Kostenki14

Levant_Neolithic

Mbuti (Mbuti.DG x3 from Fu et al.)

Papuan

Satsurblia

Ust_Ishim

Villabruna


If you’re seeing “infeasible”, then remove the redundant reference population that might be causing problems, usually Yoruba or Nganasan, and run again. If it’s still not working, then maybe your dataset is just too different in some way, perhaps with not enough markers (there should be around 200K SNPs available for these runs). See also… qpAdm tour of Europe: the Bronze Age invasion Source Eurogenes Blog


HiPOD (7 January 2018): Southern Fissures  252 km above the…


HiPOD (7 January 2018): Southern Fissures


  252 km above the surface.


Images and posts from HiRISE, the high resolution camera onboard the Mars Reconnaissance Orbiter (MRO, NASA).


Jewelry and metal workshop, from a rare record of frescoes…


Jewelry and metal workshop, from a rare record of frescoes from Thebes, recorded 1819 on his second visit to Egypt by Frédéric Cailliaud (1787-1869).


Top left shows men smelting metal. Top right shows molten metal being poured in to molds. Bottom left shows men blowing on fire for heat. Bottom right shows threading of beads on to papyrus fibers to create collars worn on special occasions. Holes are created in the beads for threading through the use of a bow drill. A bow drill was made with reed and string pulled back and forth to drill a hole with a sharp flint into the glass bead blowing on to coals, bottom. Note use of canes to hold over fire.


The Sphinx, 1887, photo taken before the Sphinx was excavated…


The Sphinx, 1887, photo taken before the Sphinx was excavated in 1920’s, head of a human and body of a lion.


Sanctuary of the Temple of Abu Simbel, from “Egypt and…


Sanctuary of the Temple of Abu Simbel, from “Egypt and Nubia”, Vol.1


David Roberts (Scottish, 1796-1864)


Pyramidal seal, Ancient Near Eastern ArtMedium: Chert,…


Pyramidal seal, Ancient Near Eastern Art


Medium: Chert, white


Bequest of Richard B. Seager, 1926

Metropolitan Museum of Art, New York, NY


http://www.metmuseum.org/art/collection/search/322552


Spouted bowl in the shape of a conch shell, Ancient Near Eastern…


Spouted bowl in the shape of a conch shell, Ancient Near Eastern Art


Medium: Gypsum alabaster


Purchase, Mrs. Vladimir S. Littauer Gift, 1970

Metropolitan Museum of Art, New York, NY


http://www.metmuseum.org/art/collection/search/325254


archaicwonder: Drachm from Zankle-Messana, Sicily c. 525–494/3…



archaicwonder:



Drachm from Zankle-Messana, Sicily c. 525–494/3 BC


Obverse: Dolphin leaping to left, within a sickle-shaped harbor, surrounded by dots. Inscription in Greek. Reverse: Scallop shell in the middle of an incuse pattern of raised and sunk squares and triangles.


Founded by Greek colonists in the 8th century BC, Messana (map) was originally called Zankle, from the Greek: ζάγκλον meaning “scythe” because of the shape of its natural harbour. Alternatively, a legend attributes the name to King Zanclus, the legendary first king of Messana. Whichever is true, the sickle shape of their harbor is reflected on the city’s coinage. In 494 BC while the Zanklian army was on campaign, the town was seized by refugees from Samos with the help of Anaxilas, the tyrant of Rhegium. The dispossessed locals turned to Hippocrates of Gela for help. He sent an army to their aid but then betrayed and enslaved them. In 488/7 BC Anaxilas tired of the Samians and expelled them, then founded a new city at Zankle and named it Messana, in honor of his original homeland in the Peloponnese.



Gordon C. Davies


Gordon C. Davies


St. Paul and St. Peter, 1595, El GrecoSize: 91.8×116 cmMedium:…


St. Paul and St. Peter, 1595, El Greco


Size: 91.8×116 cm
Medium: oil, canvas


Portrait of a Windisch farmer, Albrecht Durer


Portrait of a Windisch farmer, Albrecht Durer


Paradies, 1579, TintorettoSize: 362×143 cmMedium: oil, canvas


Paradies, 1579, Tintoretto


Size: 362×143 cm
Medium: oil, canvas


Venezuelan rock art mapped in unprecedented detail

archaeologicalnews:




Rock engravings located in Western Venezuela – including some of the largest recorded anywhere in the world – have been mapped in unprecedented detail by UCL researchers.


The engravings (petroglyphs), some of which are thought to be up to 2,000 years old, include depictions of animals, humans and cultural rituals. One panel is 304m² containing at least 93 individual engravings, the largest of which measure several metres across. Another engraving of a horned snake measures more than 30 metres in length.


All the rock art surveyed is located in the Atures Rapids (Raudales de Atures) area of Amazonas state in Venezuela, historically reported as the home of the native Adoles by Jesuit priests. Eight groups of engraved rock art were recorded on five islands within the Rapids. Read more.



13 Reasons to Have an Out of This World Friday (the 13th)

1. Know that not all of humanity is bound to the

ground


image

Since 2000, the International

Space Station has been continuously occupied by humans. There, crew members

live and work while conducting important research that benefits life on Earth

and will even help us eventually travel to deep space destinations, like Mars.


2. Smart people are up all night working in control

rooms all over NASA to ensure that data keeps flowing from our satellites and

spacecraft


image

Our satellites and spacecraft help scientists study Earth

and space. Missions looking toward Earth provide information about clouds,

oceans, land and ice. They also measure gases in the atmosphere, such as ozone

and carbon dioxide, and the amount of energy that Earth absorbs and emits. And

satellites monitor wildfires, volcanoes and their smoke.


image

Satellites and spacecraft that

face toward space have a variety of jobs. Some watch for dangerous rays coming

from the sun. Others explore asteroids and comets, the history of stars, and

the origin of planets. Some fly near or orbit other planets. These spacecraft

may look for evidence of water on Mars or capture close-up pictures of Saturn’s

rings.


3. The spacecraft, rockets and systems developed to

send astronauts to low-Earth orbit as part our Commercial Crew Program is also

helping us get to Mars


Changes to the human body during

long-duration spaceflight
are significant challenges to solve ahead of a

mission to Mars and back. The space station allows us to perform long duration

missions without leaving Earth’s orbit.


image

Although they are orbiting

Earth, space station astronauts spend months at a time in near-zero gravity,

which allows scientists to study several physiological changes and test

potential solutions. The more time they spend in space, the more helpful the

station crew members can be to those on Earth assembling the plans to go to

Mars.


4. Two new science missions will travel where no

spacecraft has gone before…a Jupiter Trojan asteroid and a giant metal

asteroid!


image

We’ve selected

two missions
that have the potential to open new windows on one of the earliest

eras in the history of our solar system
– a time less than 10 million years

after the birth of our sun!


image

The first mission, Lucy, will

visit six of Jupiter’s mysterious Trojan asteroids. The Trojans are thought to

be relics of a much earlier era in the history of the solar system, and may

have formed far beyond Jupiter’s current orbit.


image

The second mission, Psyche,

will study a unique metal asteroid that’s never been visited before. This giant

metal asteroid, known as 16 Psyche, is about three times farther away from the

sun than is the Earth. Scientists wonder whether Psyche could be an exposed

core of an early planet that could have been as large as Mars, but which lost

its rocky outer layers due to a number of violent collisions billions of years

ago.


5. Even astronauts eat their VEGGIES’s


NASA astronaut Shane

Kimbrough

collected the third and final harvest
of the latest round of the Veggie

investigation, testing the capability to grow fresh vegetables on the

International Space Station.


image

Understanding how plants respond to microgravity

is an important step for future long-duration space missions, which will require

crew members to grow their

own food
. Crew members have previously grown

lettuce
and flowers

in the Veggie

facility
. This new series of the study expands on previous validation

tests.


6. When you feel far away from home, you can think of

the New Horizons spacecraft as it heads toward the Kuiper Belt, and the Voyager

spacecrafts are beyond the influence of our sun…billions of miles away


image

Our New Horizons spacecraft completed its Pluto flyby in

July 2015 and has continued on its way toward the Kuiper Belt. The spacecraft continues to send back

important data as it travels toward deeper space at more than 32,000 miles per

hour, and is nearly 3.2 billion miles from Earth.


image

In addition to New Horizons,

our twin Voyager

1 and 2 spacecraft
are exploring where nothing from Earth has flown before.

Continuing on their more-than-37-year journey since their 1977 launches, they

are each much farther away from Earth and the sun than Pluto. In August 2012, Voyager

1 made the historic entry into interstellar space, the region between the

stars, filled with material ejected by the death of nearby stars millions of

years ago.


7. Earth has a magnetic field that largely protects it

from the solar wind stripping away out atmosphere…unlike Mars


image

Findings from our MAVEN mission have identified the process that appears

to have played a key role in the transition of the Martian climate from an early, warm

and wet environment to the cold, arid planet Mars is today. MAVEN data have

enabled researchers to determine the rate at which the Martian atmosphere

currently is losing gas to space via stripping by the solar wind. Luckily,

Earth has a magnetic field that largely protects it from this process.


8. There are humans brave enough to not only travel in

space, but venture outside space station to perform important repairs and

updates during spacewalks


image

Spacewalks

are
important events where crew members repair, maintain and upgrade parts

of the International Space Station. These activities can also be referred to as

EVAs – Extravehicular Activities. Not only do spacewalks require an enormous

amount of work to prepare for, but they are physically demanding on the

astronauts. They are working in the vacuum of space in only their spacewalking

suit.


image

When on a spacewalk,

astronauts use safety tethers to stay close to their spacecraft. One end of the

tether is hooked to the spacewalker, while the other end is connected to the

vehicle. Spacewalks typically last around 6.5 hours, but can be extended to 7

or 8 hours, if necessary.


9. We’re working to create new aircraft that will dramatically

reduce fuel use, emissions and noise…meaning we could change the way you fly! 


image

The nation’s airlines could

realize more than $250

billion dollars in savings
in the near future thanks to green-related

technologies that we are developing and refining. These new technologies could

cut airline fuel use in half, pollution by 75% and noise to nearly one-eighth

of today’s levels!


10. You can see a global image of your home planet…EVERY

DAY


image

Once a day, we will post at

least a dozen new color images of Earth acquired from 12 to 36 hours

earlier. These images are taken by our EPIC camera from one million miles away

on the Deep Space Climate Observatory (DSCOVR). Take a look HERE.


11. Employees of NASA have always been a mission

driven bunch, who try to find answers that were previously unknown


The film “Hidden Figures,”

focuses on the stories of Katherine Johnson, Mary Jackson and Dorothy Vaughan,

African-American women who were essential to the success of early spaceflight.



Today, we embrace their

legacy and strive to include everyone who wants to participate in our ongoing

exploration. In the 1960’s, we were on an ambitious journey to the moon, and

the human computers portrayed in Hidden Figures helped get us there. Today, we

are on an even more ambitious journey to Mars. We are building a vibrant,

innovative workforce that reflects a vast diversity of discipline and thought,

embracing and nurturing all the talent we have available, regardless of gender,

race or other protected status. Take a look at our Modern Figures HERE.


12. A lot of NASA-developed tech has been transferred

for use to the public



Our Technology Transfer Program highlights technologies

that were originally designed for our mission needs, but have since been

introduced to the public market. HERE are a few spinoff technologies that you might not

know about.


13. If all else fails, here’s an image of what we

(Earth) and the moon look like from Mars  


image

From the most powerful

telescope orbiting Mars comes a new

view of Earth and its moon
, showing continent-size detail on the planet and

the relative size of the moon. The image combines two separate exposures taken

on Nov. 20 by our High

Resolution Imaging Science Experiment (HiRISE)
camera on our Mars Reconnaissance Orbiter.


In the image, the reddish feature near the

middle of the face of Earth is Australia.


Source NASA blog


The Most Amazing Paracas Elongated Skull Found So Far; New Born Baby


What you are looking at, above, is the mummified head and partial neck of a baby from the Paracas culture of Peru that died between 2000 and 2800 years ago, as that was the lifespan of that coastal culture. It was likely a newborn, or perhaps 3 months old at the time of death.



The arrows above indicate the positions of the eye sockets and mouth. As you can see, the skull is extremely elongated, and could well indicate that this child was born with a naturally, and genetically elongated head, and not the result of cranial deformation.



The arrow in the above photo points to the very fine hair of the baby, which is auburn red in colour; not the typical jet black colour of Native American people. This, along with the elongation, shows clear genetic differentiation from what one would normally expect.



Again, the photo above shows the positioning of the left eye socket and mouth. DNA testing of this individual is presently under consideration, to be conducting via the correct channels and protocols.



Finally, note, in the above photo and on the left, the position of the vertebral column. It is much further to the back of the skull than normal, and could well indicate that it is an evolutionary adaptation to compensate for the elongated skull.



Join us in August 2017, for a unique tour that explores the amazing ancient elongated skulls of Peru. Full details HERE.



The definitive book on the subject of the elongated skulls of Peru and Bolivia. Buy it HERE in e-book or paperback format


The post The Most Amazing Paracas Elongated Skull Found So Far; New Born Baby appeared first on Hidden Inca Tours.


Collapsing Rome Rome was neither built in a day, nor was it…


Collapsing Rome


Rome was neither built in a day, nor was it always built over the best places. Humans have been living in the city of Rome for thousands of years and have a habit of building over former structures, such as the tunnel you’re looking at.

The Moon on April 21, 1972 – NASA calls it the “Grand Prix.” As…



The Moon on April 21, 1972 – NASA calls it the “Grand Prix.” As Apollo 16 astronaut John Young puts the Lunar Rover through its paces, spaceman Charlie Duke watches and provides color commentary: “He’s got about two wheels on the ground. There’s a big rooster tail out of all four wheels. And as he turns, he skids. The back end breaks loose just like on snow. Come on back, John. (Pause) And the DAC is running. Man, I’ll tell you, Indy’s never seen a driver like this. (Pause) Okay, when he hits the craters and starts bouncing is when he gets his rooster tail. He makes sharp turns. Hey, that was a good stop. Those wheels just locked.” (Indy meaning the Indianapolis 500.)


(NASA)


The Moon, April 23, 1972. During the final moonwalk of the…


The Moon, April 23, 1972. During the final moonwalk of the Apollo 16 mission, commander John Young does some raking near the lunar rover. (NASA)


April 27, 1972 – With an assist from a U.S. Navy diver, Apollo…


April 27, 1972 – With an assist from a U.S. Navy diver, Apollo 16 astronaut John Young exits the command module after splashing down in the Pacific.


Reliquary, European Sculpture and Decorative ArtsMedium: Gold,…


Reliquary, European Sculpture and Decorative Arts


Medium: Gold, rock crystal, enamel


Gift of J. Pierpont Morgan, 1917

Metropolitan Museum of Art, New York, NY


http://www.metmuseum.org/art/collection/search/193674


christopher-mongeau: Quechee Gorge, VT Instagram | Prints (25%…



christopher-mongeau:



Quechee Gorge, VT


Instagram | Prints (25% off today + tomorrow!)



VFX Art Scene – Stargate // Kevin Leroy




VFX Art Scene – Stargate // Kevin Leroy


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