четверг, 8 ноября 2018 г.

HiPOD (8 November 2018): Ridges in Terra Sabaea   – The…

HiPOD (8 November 2018): Ridges in Terra Sabaea

   – The objective of this observation is to determine the nature of ridges on a crater floor.  They may represent inverted terrain. (256 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

Ancient burial site and monument found in England’s New Forest

Archaeologists and volunteers have found an important prehistoric burial site near Beaulieu dating back thousands of years.

Ancient burial site and monument found in England's New Forest
The urns contained cremated human bone and had been placed into small pits
[Credit: New Forest National Park Authority via BBC]

A community dig in a field at East End set out to investigate what they thought was a Bronze Age barrow which had been ploughed over and they were thrilled to find four cremation burial urns dating from that period around 3,000 years ago.

But as the excavation progressed further, the evidence began suggesting that the site might have been an important place for even older human activity which Bronze Age settlers then adapted.

New Forest National Park Authority Community Archaeologist James Brown said: ‘We were elated to find the urns – they were inverted in what we originally thought was the ditch around the barrow and one has a decorative band pattern on it that will help us to date them. These urns were domestic pots and contain cremated human bone placed into small pits. So we know this site was a place of memorial for people in the New Forest around 3,000 years ago.

‘But we didn’t find any evidence of the barrow’s mound or any burial activity in the middle as you might expect.’

He said the lack of evidence may be the result of the barrow being ploughed out, or destroyed by the later field boundary ditches that run through the middle. The site was fully metal-detected as part of the archaeological investigation with the only finds being modern metal work in the topsoil.

‘However, there was evidence of human activity below the level of the urns’, he said.

Ancient burial site and monument found in England's New Forest
Excavations on farmland in the New Forest are rare as it is mostly sites which are being developed
which offer opportunities for archaeological digs, according to the park authority
[Credit: New Forest National Park Authority via BBC]

‘We also found two Neolithic flints from around 5,000 years ago, one of which probably would have been attached to a wooden shaft and used as a spear. Geophysics scans showed that there may have been two entrances to the site. So the evidence is strongly hinting at a much earlier Neolithic monument that was then re-used in the Bronze Age.’

Volunteer Ian Richardson, from Poole, said the volunteers were fascinated to see what the site revealed.

‘It is always good to find something when the day has been spent moving mud and stone!’ he said. ‘You get in touch with the past and think the last person to pick that up was here thousands of years ago.’

National Park Senior Archaeologist Frank Green said: ‘The archaeologists will now analyse the urns and soil and use scientific techniques to date them, conserve them and hopefully display them in the New Forest. Ongoing work will attempt to try and fully understand what might prove to be an incredibly important part of the New Forest’s prehistoric past.’

Thanks to the Beaulieu Estate and the tenant farmer, the dig provided a rare chance to excavate on farmland in the New Forest. As the Forest doesn’t get built on as much as other parts of the country there are fewer opportunities for excavation while sites are being developed.

James said: ‘This often leads people to assume that the Forest didn’t see much early human activity – it’s probably there but we just don’t get the chance to see it. So the finds at this site are already adding to our knowledge in quite a substantial way of the story of people who have lived here in the past – the residents, their lives and how they exploited the Forest landscape.’

Source: New Forest National Park Authority [November 02, 2018]



Medieval castle discovered in Poland’s Żelechów

We wanted to discover another Malbork, and we found… Biskupin, say discoverers of the late medieval castle in Żelechów (Mazowieckie). It was the seat of the noble Ciołek family; its wooden elements have been preserved to this day.

Medieval castle discovered in Poland's Żelechów
Credit: M. Legut-Pintal

The search for the castle in Żelechów lasted several years. Historians knew from a few mentions that there used to be a stronghold in this area in the Middle Ages. Now — thanks to the use of air laser scanning and other methods that do not even require driving the blade into the ground — they precisely located the lost structure. It is located north-west of the Żelechów market square, near fishponds.

“We knew that the castle existed, although information about its location, size and construction was not preserved anywhere”, says the archaeological project leader Wojciech Bis from the Institute of Archaeology and Ethnology PAS.

The historian involved in the project, Michał Zbieranowski from the Institute of History PAS emphasizes that the castle was the seat of the Ciołek family. “Unfortunately, we do not have a lot of information about it, because written sources were burned at the end of World War II”, he adds.

In previous years, researchers located remains of the structure. Small scale excavations started last year, but only this year`s digs brought surprising results. “We wanted to discover another Malbork, and we found… another Biskupin”, says Zbieranowski.

Medieval castle discovered in Poland's Żelechów
Credit: P. Cembrzyński

Medieval castle discovered in Poland's Żelechów
Credit: W. Bis

This, of course, is not a reference to the age of the castle (which is about 2,200 years younger than the one in Biskupin) — but to the material from which it was built.

Scientists previously believed that there were massive brick or stone remains of the object’s foundations underground. That conclusion was based on the results of geophysical research. But excavations revealed something else. “It turned out that the complex was not surrounded by a wall, only a rampart reinforced with stone structures. Many elements of wooden buildings have been exposed. They are very well preserved, especially the foundations of some houses around the castle’s court. This is due to the high level of ground water, which it makes our work difficult, but preserves organic material”, says Bis.

The preserved elements include door seats, beams forming external walls and traces of fixing boards to internal walls.

“Oak beams have been preserved so well that you can get the impression that it is a modern structure”, emphasises Zbieranowski. Expert analysis allowed to precisely determine the age of wood used for construction — it comes from approx. 1466.

Medieval castle discovered in Poland's Żelechów
Credit: W. Bis

Medieval castle discovered in Poland's Żelechów
Credit: W. Bis

“When we imagine a ‘castle’, we see a stronghold made of stone or bricks, but they were not always made of these materials! In the Middle Ages, wood-and-earth fortifications worked equally well. In the case of Mazowsze, it was easy to obtain very durable oak wood, which was easily accessible in that area”, says Bis.

Thanks to the latest research, we now know that the seat of the Ciołek family had a regular, four-sided shape. Over time, it was expanded and enlarged. At first it was an object about 50 by 50 meters, later — 85 by 90 meters. Defences of the fortress included a wide, wet moat surrounding the whole complex. For now, archaeologists have carried out excavations in a small area. Although most of the structures within the fort were built of wood, in one place the researchers also found massive stone foundations.

“These could be the remains of a brick mansion of the owner of this fort”, Bis suggests.

Stove tiles are among the objects that indicate that the fortress had wealthy inhabitants. Various and decorated tiles indicate that there were least several furnaces in the living quarters. Similar monuments are known from other mansions of nobles. “Tiles with similar ornamentation are known from Podlasie, from the court of King Sigismund II Augustus in Knyszyn, as well as the castle in Tykocin”, says Bis.

Medieval castle discovered in Poland's Żelechów
Credit: W. Bis

The castle was not lucky. It was probably founded shortly aster 1450, but it was probably abandoned already in the beginning of the 16th century. According to the scientists, feuds between the magnates contributed to this. The seat of the Ciołek family was temporarily taken over by Feliks from Zielanka.

“We have uncovered numerous traces of burning, burnt fragments of vessels, and even a cannonball. These could be traces of attempts to take back the castle by the Ciołeks. We hope that the excavations planned for the next years will shed new light on this issue”, adds Zbieranowski.

Researchers also hope that their work will help change the image of this region of Mazowsze in the Middle Ages and in the early modern period. Until now, probably due to the shortage of written sources and the lack of archaeological research, it was generally believed that only a few people lived in this area at that time. Meanwhile, the preliminary field survey researchers shows that there may be at least several similar, unknown and fortified residences from this period in this area.

Author: Szymon Zdziebłowski | Source: PAP – Science in Poland [November 02, 2018]



Ancient copper smelting furnaces discovered near Apollonia Pontica

Ceramic kilns for smelting copper ore dating to the second half of the 6th century BC have been discovered in the ancient Greek city of Apollonia Pontica near the Black Sea town of Sozopol (Sozopolis) in southeast Bulgaria.

Ancient copper smelting furnaces discovered near Apollonia Pontica
Several kilns have been found at the site of the ancient copper mine near Apollonia Pontica,
today’s Sozopol on the Black Sea coast in Southeast Bulgaria [Credit: Darik Burgas]

The kilns were found close to an ancient copper mine in an area known as Medni Rid (Copper Ridge) by a team of Bulgarian and German archaeologists led by Petar Leshtakov and Krasimir Nikov.

“The [kilns] demonstrate the highly developed and specialized organization of copper ore extraction and processing within the very mine,” says Dimitar Nedev, Director of the Sozopol Museum of Archaeology.

The digs started as rescue excavations in October 2018 after tree logging trucks compromised the terrain, Nedev reveals.

“This discovery is of extreme significance for Bulgarian archaeology, and perhaps one of the major archaeological events of 2018,” the local museum director said.

The discovery marks the first time ancient metallurgy furnaces have been found near Bulgaria’s Sozopol but outside the immediate territory of the ancient polis.

Amphorae and other pottery imported from the Greek islands of Chios and Samos recovered at the site indicate that copper ore extraction and processing began shortly after the founding of Apollonia Pontica in the early seventh century BC.

The furnaces were found on the northern slope of  ‘Copper Ridge’, and are two types: the first was used for ‘frying’, that is, removing the sulfur from the copper ore concentrate; the second type were the melting kilns.

The copper ore in ‘Copper Ridge’ was extracted in an open-air mine, without shafts or tunnels, with a diametre of about 1.2 kilometres.

The researchers believe they have also identified three more groups of kilns in the area, and are hopeful of locating the miners’ camp.

Source: Archaeology in Bulgaria [November 02, 2018]



Evidence of outburst flooding indicates plentiful water on early Mars

The presence of water on Mars has been theorized for centuries. Early telescopes revealed ice caps, and early astronomers noted channels that were hypothesized to be natural rivers or creature-created canals.

Evidence of outburst flooding indicates plentiful water on early Mars
The physiography of Gale Crater shown in a HiRISE map
[Credit: Geological Society of America]

Over the past two decades, rovers Sojourner, Spirit, Opportunity, and Curiosity have sent back invaluable data to scientists who are trying to interpret the planet’s surface and uncover evidence of past or present water.

Since its landing on the “Red Planet” in August of 2012, Curiosity Rover has traveled about 20 kilometers within Gale Crater. The rover has examined about 400 meters of sedimentary rock that exists in the crater, says Ezat Heydari of Jackson State University in Jackson, Mississippi — including rocks thought to be 3.7 to 4.1 billion years old (Noachian time).

Heydari and colleagues used these images of sedimentary rocks to interpret the geologic processes that occurred billions of years ago on Mars. He is presenting their findings on Sunday at the Geological Society of America Annual Meeting in Indianapolis, Indiana.

Within those 400 meters of rock, the researchers identified four different units that represent different types of deposition, and Heydari says that “in my opinion, deposition of all of these packages involved water.”

Evidence of outburst flooding indicates plentiful water on early Mars
Geology within the landing ellipse of the Curiosity Rover. The Hummocky Plains Unit, the sedimentary rock unit
that contains cross bedded conglomerate thought to be deposited in an outburst flood, is shown in sage green
[Credit: Geological Society of America]

One of those packages, called the Hummocky Plain Unit, is a conglomerate with grains up to 20 centimeters in size. The Curiosity images showed ridges in the Hummocky Plain Unit, filled with rounded cobbles and cross beds reaching 4 meters high — indications that deposition was done by moving water.

In addition, some of the images have height information that can create a topographic profile of the surface, revealing the profiles of the ridges. “These ridges are asymmetric,” says Heydari. “In other words, they were formed by one directional current.”

After seeing the images, Heydari says he immediately thought of the Channelized Scablands in Washington State. The Mars ridges are equally spaced, he says, adding that they are about twice the size of those in the Scablands. The ridges on Mars and Earth had similar characteristics, but it wasn’t until he saw the cross beds that Heydari concluded the Mars deposits were made by large-scale flooding.

Using comparisons to Earth rivers, Heydari notes that to create cross beds 4 meters high, the flowing water would have been about 10 to 20 meters deep. “That’s one of the reasons I say these deposits are related to floods, rather than a puny river,” he says.

Evidence of outburst flooding indicates plentiful water on early Mars
Close up of a Mastcam image mosaic (Mcam02603) acquired on Sol 620. This conglomerate
 has grains up to 10 centimeters in diameter and some are well rounded. The grains also
 are part of a 2-meter-high cross bed [Credit: Geological Society of America]

Heydari says that the Noachian sedimentary rocks found in Gale Crater may have been deposited in a similar setting as Pleistocene Earth (about 2 million years to 12,000 years ago), with large-scale global ice and dramatic outburst floods.

“On both planets, one hemisphere was covered by ice — northern Hemisphere on Earth, versus the Southern Hemisphere in Mars — and the other hemisphere was warm,” says Heydari. He adds that this comparison is important because it shows that ancient Mars appears to be very similar to Pleistocene Earth, where liquid water is stable and able to support life.

Source: Geological Society of America [November 05, 2018]



Scientist finds elusive star with origins close to Big Bang

Astronomers have found what could be one of the universe’s oldest stars, a body almost entirely made of materials spewed from the Big Bang.

Scientist finds elusive star with origins close to Big Bang
The star, named 2MASS J18082002–5104378 B, is part of a two-star system orbiting around a common point

The discovery of this approximately 13.5 billion-year-old tiny star means more stars with very low mass and very low metal content are likely out there — perhaps even some of the universe’s very first stars.

The star is unusual because unlike other stars with very low metal content, it is part of the Milky Way’s “thin disk” — the part of the galaxy in which our own sun resides. And because this star is so old, researchers say it’s possible that our galactic neighborhood is at least 3 billion years older than previously thought.

“This star is maybe one in 10 million,” said lead author Kevin Schlaufman, a Johns Hopkins University assistant professor of physics and astronomy. “It tells us something very important about the first generations of stars.”

The universe’s first stars after the Big Bang would have consisted entirely of elements like hydrogen, helium, and small amounts of lithium. Those stars then produced elements heavier than helium in their cores and seeded the universe with them when they exploded as supernovae.

Scientist finds elusive star with origins close to Big Bang
The new discovery is only 14 percent the size of the sun and is the new record holder for the star with the smallest
complement of heavy elements. It has about the same heavy element complement as Mercury,
the smallest planet in our solar system [Credit: Kevin Schlaufman/JHU]

The next generation of stars formed from clouds of material laced with those metals, incorporating them into their makeup. The metal content, or metallicity, of stars in the universe increased as the cycle of star birth and death continued.

The newly discovered star’s extremely low metallicity indicates that, in a cosmic family tree, it could be as little as one generation removed from the Big Bang. Indeed, it is the new record holder for the star with the smallest complement of heavy elements — it has about the same heavy element content as the planet Mercury. In contrast, our sun is thousands of generations down that line and has a heavy element content equal to 14 Jupiters.

Astronomers have found around 30 ancient “ultra metal-poor” stars with the approximate mass of the sun. The star Schlaufman and his team found, however, is only 14 percent the mass of the sun.

The star is part of a two-star system orbiting around a common point. The team found the tiny, almost invisibly faint “secondary” star after another group of astronomers discovered the much brighter “primary” star. That team measured the primary’s composition by studying a high-resolution optical spectrum of its light. The presence or absence of dark lines in a star’s spectrum can identify the elements it contains, such as carbon, oxygen, hydrogen, iron, and more. In this case, the star had extremely low metallicity. Those astronomers also identified unusual behavior in the star system that implied the presence of a neutron star or black hole. Schlaufman and his team found that to be incorrect, but in doing so, they discovered the visible star’s much smaller companion.

The existence of the smaller companion star turned out to be the big discovery. Schlaufman’s team was able to infer its mass by studying the primary star’s slight “wobble” as the little star’s gravity tugged at it.

As recently as the late 1990s, researchers believed that only massive stars could have formed in the earliest stages of the universe — and that they could never be observed because they burn through their fuel and die so quickly.

But as astronomical simulations became more sophisticated, they began to hint that in certain situations, a star from this time period with particularly low mass could still exist, even more than 13 billion years since the Big Bang. Unlike huge stars, low-mass ones can live for exceedingly long times. Red dwarf stars, for instance, with a fraction of the mass of the sun, are thought to live to trillions of years.

The discovery of this new ultra metal-poor star, named 2MASS J18082002-5104378 B, opens up the possibility of observing even older stars.

“If our inference is correct, then low-mass stars that have a composition exclusively the outcome of the Big Bang can exist,” said Schlaufman, who is also affiliated with the university’s Institute for Data Intensive Engineering and Science. “Even though we have not yet found an object like that in our galaxy, it can exist.”

The findings are published in The Astrophysical Journal.

Source: Johns Hopkins University [November 05, 2018]



An ice age lasting 115,000 years in two minutes

An international research team used a computer model to reconstruct the history of glaciation in the Alps, visualising it in a two-minute computer animation. The simulation aims to enable a better understanding of the mechanisms of glaciation.

An ice age lasting 115,000 years in two minutes
Today only the high Alpine peaks and their surroundings are still glaciated—in the picture the Piz Palu
in the Upper Engadine (to the right of the centre of the picture) [Credit: Peter Ruegg]

Around 115,000 years ago, the last glacial period in the earth’s history began. It was an eventful time, as glaciers advanced from the Alps onto the Swiss Plateau, retreated, and then advanced again. In the process, the powerful ice flows carved out valleys, such as the Rhone Valley, bringing rock debris—ranging in size from fine sediment to boulders weighing several tonnes—across the landscape with them. This debris, deposited as moraines, formed the lush, green foothills of the Alps. The heavy boulders, known as erratics, can be found spread out across the Swiss Plateau, in Alpine valleys and in the Jura Mountains.
Three hundred years of glacial history research

Despite the fact that explorers and scientists have been researching the glacial history of the Alps for almost 300 years, no one has previously succeeded in unequivocally identifying which climate developments led to large-scale glaciation. Questions remained about what conditions affected how the glaciers expanded, how thick the ice was, how often the ice sheet expanded and retreated, and what caused the ice to expand at different rates in different Alpine regions.

To gain a better understanding of all this, Julien Seguinot from ETH Zurich’s Laboratory of Hydraulics, Hydrology and Glaciology, together with several colleagues, simulated glacier development in the Alps over the last 120,000 years on the CSCS supercomputer “Piz Daint”. Their study was recently published in the journal The Cryosphere.

To simulate ice build-up and glacier spread, they used a special model (Parallel Ice Sheet Model, or PISM) that they fed with data about the initial topography of mountain ranges and glaciers, the physical properties of rock and glaciers based partly on observations from the Antarctic and Greenland, heat flow from the earth’s interior, and the climatic conditions. They based the latter on present-day weather data combined with paleo-climate records deduced from sediment and ice cores from the last 120,000 years.

More glacier movement than previously thought

The scientists conducted simulations with three different sets of paleo-climate data, as well as two different precipitation scenarios. Only one of the climate data sets delivered results that match the geological evidence left behind by the glaciers in rock and sediment. The results of this simulation indicate that Alpine glaciers advanced and retreated more often than previously thought. For a long time, glaciologists assumed a minimum of four glaciations. Since the 1980s, however, this low figure has often been called into question. The new simulation appears to support the theory of more frequent glaciations, showing that some Alpine glaciers may have advanced and retreated more than 10 times during the last 120,000 years.

According to the model, the glaciers expanded furthest around 25,000 years ago and advanced into the foothills of the Alps, reaching Bern, Zurich and the Lake Constance region including Schaffhausen in Switzerland, and spreading east almost to Munich in Germany. Over the course of a few more thousand years, the glacial period then gradually turned into the current interglacial period—this can also be seen in the researchers’ video. These glacial and interglacial periods alternate during an ice age. The earth is currently in the middle of an ice age, which is defined as when at least one of the earth’s poles is covered by ice.

Underestimated ice thickness

Using a detailed analysis of another simulation that charts the glaciation of the last 120,000 years down to the kilometre, the researchers conclude that during peak glaciation, the ice may have been much thicker than previously thought: in the upper Rhone Valley, for example, it may have been up to 800 metres thicker.

The researchers admit that the results are limited due to uncertainties caused by the simplified description of the processes between glacier and ground, as well as the climate conditions. For Seguinot, however, the main difficulty with the study was in interpreting the available data of glacier traces such as moraines, erratics and the direction of ice flow gathered over the last 300 years. “By using glacier models like PISM on supercomputers such as Piz Daint, we are able to reconstruct the history of glaciation with an unprecedented level of detail,” says Seguinot. Validating such results, however, requires more and systematically gathered data in digital maps across both national and language borders.

Source: ETH Zurich [November 06, 2018]



Chew on this: Two new studies reveal secrets of early dinosaur…

Chew on this: Two new studies reveal secrets of early dinosaur and mammal tooth evolution http://www.geologypage.com/2018/11/chew-on-this-two-new-studies-reveal-secrets-of-early-dinosaur-and-mammal-tooth-evolution.html

Tiniest ever fossil ape discovered in Kenya…

Tiniest ever fossil ape discovered in Kenya http://www.geologypage.com/2018/11/tiniest-ever-fossil-ape-discovered-in-kenya.html

Tiny, ancient fossil shows evidence of the breath of life…

Tiny, ancient fossil shows evidence of the breath of life http://www.geologypage.com/2018/11/tiny-ancient-fossil-shows-evidence-of-the-breath-of-life.html

The teeth of Changchunsaurus: Rare insight into ornithopod…

The teeth of Changchunsaurus: Rare insight into ornithopod dinosaur tooth evolution http://www.geologypage.com/2018/11/the-teeth-of-changchunsaurus-rare-insight-into-ornithopod-dinosaur-tooth-evolution.html

Scientists theorize new origin story for Earth’s water…

Scientists theorize new origin story for Earth’s water http://www.geologypage.com/2018/11/scientists-theorize-new-origin-story-for-earths-water.html

2018 November 8 Mars in the Loop Image Credit & Copyright:…

2018 November 8

Mars in the Loop
Image Credit & Copyright: Tunc Tezel (TWAN)

Explanation: This composite of images spaced some 5 to 9 days apart, from late April (bottom right) through November 5 (top left), traces the retrograde motion of ruddy-colored Mars through planet Earth’s night sky. To connect the dots and dates in this 2018 Mars retrograde loop, just slide your cursor over the picture (and check out this animation). But Mars didn’t actually reverse the direction of its orbit. Instead, the apparent backwards motion with respect to the background stars is a reflection of the motion of the Earth itself. Retrograde motion can be seen each time Earth overtakes and laps planets orbiting farther from the Sun, the Earth moving more rapidly through its own relatively close-in orbit. On July 27, Mars was near its favorable 2018 parihelic opposition, when Mars was closest to the Sun in its orbit while also opposite the Sun in Earth’s sky. For that date, the frame used in this composite was taken during the total lunar eclipse.

∞ Source: apod.nasa.gov/apod/ap181108.html

Astronomers Unveil Growing Black Holes in Colliding Galaxies

Galaxy Mergers 

NASA, ESA, and M. Koss (Eureka Scientific, Inc.); Hubble image: NASA, ESA, and M. Koss (Eureka Scientific, Inc.); Keck images: W. M. Keck Observatory and M. Koss (Eureka Scientific, Inc.); Pan-STARRS images: Panoramic Survey Telescope and Rapid Response System and M. Koss (Eureka Scientific, Inc.). Release images

Peering through thick walls of gas and dust surrounding the messy cores of merging galaxies, astronomers are getting their best view yet of close pairs of supermassive black holes as they march toward coalescence into mega black holes.

A team of researchers led by Michael Koss of Eureka Scientific Inc., in Kirkland, Washington, performed the largest survey of the cores of nearby galaxies in near-infrared light, using high-resolution images taken by NASA’s Hubble Space Telescope and the W. M. Keck Observatory in Hawaii. The Hubble observations represent over 20 years’ worth of snapshots from its vast archive.

“Seeing the pairs of merging galaxy nuclei associated with these huge black holes so close together was pretty amazing,” Koss said. “In our study, we see two galaxy nuclei right when the images were taken. You can’t argue with it; it’s a very ‘clean’ result, which doesn’t rely on interpretation.”

The images also provide a close-up preview of a phenomenon that must have been more common in the early universe, when galaxy mergers were more frequent. When galaxies collide, their monster black holes can unleash powerful energy in the form of gravitational waves, the kind of ripples in space-time that were just recently detected by ground-breaking experiments.

The new study also offers a preview of what will likely happen in our own cosmic backyard, in several billion years, when our Milky Way combines with the neighboring Andromeda galaxy and their respective central black holes smash together.

“Computer simulations of galaxy smashups show us that black holes grow fastest during the final stages of mergers, near the time when the black holes interact, and that’s what we have found in our survey,” said study team member Laura Blecha of the University of Florida, in Gainesville. “The fact that black holes grow faster and faster as mergers progress tells us galaxy encounters are really important for our understanding of how these objects got to be so monstrously big.”

A galaxy merger is a slow process lasting more than a billion years as two galaxies, under the inexorable pull of gravity, dance toward each other before finally joining together. Simulations reveal that galaxies kick up plenty of gas and dust as they undergo this slow-motion train wreck.

The ejected material often forms a thick curtain around the centers of the coalescing galaxies, shielding them from view in visible light. Some of the material also falls onto the black holes at the cores of the merging galaxies. The black holes grow at a fast clip as they engorge themselves with their cosmic food, and, being messy eaters, they cause the infalling gas to blaze brightly. This speedy growth occurs during the last 10 million to 20 million years of the union. The Hubble and Keck Observatory images captured close-up views of this final stage, when the bulked-up black holes are only about 3,000 light-years apart — a near-embrace in cosmic terms.

It’s not easy to find galaxy nuclei so close together. Most prior observations of colliding galaxies have caught the coalescing black holes at earlier stages when they were about 10 times farther away. The late stage of the merger process is so elusive because the interacting galaxies are encased in dense dust and gas and require high-resolution observations in infrared light that can see through the clouds and pinpoint the locations of the two merging nuclei.

The team first searched for visually obscured, active black holes by sifting through 10 years’ worth of X-ray data from the Burst Alert Telescope (BAT) aboard NASA’s Neil Gehrels Swift Telescope, a high-energy space observatory. “Gas falling onto the black holes emits X-rays, and the brightness of the X-rays tells you how quickly the black hole is growing,” Koss explained. “I didn’t know if we would find hidden mergers, but we suspected, based on computer simulations, that they would be in heavily shrouded galaxies.Therefore we tried to peer through the dust with the sharpest images possible, in hopes of finding coalescing black holes.”

The researchers combed through the Hubble archive, identifying those merging galaxies they spotted in the X-ray data. They then used the Keck Observatory’s super-sharp, near-infrared vision to observe a larger sample of the X-ray-producing black holes not found in the Hubble archive.

“People had conducted studies to look for these close interacting black holes before, but what really enabled this particular study were the X-rays that can break through the cocoon of dust,” Koss said. “We also looked a bit farther in the universe so that we could survey a larger volume of space, giving us a greater chance of finding more luminous, rapidly growing black holes.”

The team targeted galaxies with an average distance of 330 million light-years from Earth. Many of the galaxies are similar in size to the Milky Way and Andromeda galaxies. The team analyzed 96 galaxies from the Keck Observatory and 385 galaxies from the Hubble archive found in 38 different Hubble observation programs. The sample galaxies are representative of what astronomers would find by conducting an all-sky survey.

To verify their results, Koss’s team compared the survey galaxies with 176 other galaxies from the Hubble archive that lack actively growing black holes. The comparison confirmed that the luminous cores found in the researchers’ census of dusty interacting galaxies are indeed a signature of rapidly growing black-hole pairs headed for a collision.

When the two supermassive black holes in each of these systems finally come together in millions of years, their encounters will produce strong gravitational waves. Gravitational waves produced by the collision of two stellar-mass black holes have already been detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO). Observatories such as the planned NASA/ESA space-based Laser Interferometer Space Antenna (LISA) will be able to detect the lower-frequency gravitational waves from supermassive black-hole mergers, which are a million times more massive than those detected by LIGO.

Future infrared telescopes, such as NASA’s planned James Webb Space Telescope and a new generation of giant ground-based telescopes, will provide an even better probe of dusty galaxy collisions by measuring the masses, growth rate, and dynamics of close black-hole pairs. The Webb telescope may also be able to look in mid-infrared light to uncover more galaxy interactions so encased in thick gas and dust that even near-infrared light cannot penetrate them.

The team’s results will appear online in the Nov. 7, 2018, issue of the journal Nature.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

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Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu

Michael Koss
Eureka Scientific Inc., Kirkland, Washington

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Two Neolithic Tridents, Tullie House Museum and Gallery, Carlisle, Cumbria, 4.11.18.The...

Two Neolithic Tridents, Tullie House Museum and Gallery, Carlisle, Cumbria, 4.11.18.

The two wooden tridents are of unknown purpose, potentially used for hunting or farming. They are made from single pieces of oak.

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Prehistoric Quernstones, Tullie House Museum and Gallery, Carlisle, Cumbria, 4.11.18.A...

Prehistoric Quernstones, Tullie House Museum and Gallery, Carlisle, Cumbria, 4.11.18.

A selection of different types of prehistoric quernstones through the Bronze and Iron Ages.

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Cosmic Detective Work: Why We Care About Space Rocks

NASA logo.

Nov. 7, 2018

Animation above: The small worlds of our solar system help us trace its history and evolution, including comets. This video clip was compiled from images taken by NASA’s EPOXI mission spacecraft during its flyby of comet Hartley 2 on Nov. 4, 2010. Animation Credits: NASA/JPL-Caltech/UMD.

The entire history of human existence is a tiny blip in our solar system’s 4.5-billion-year history. No one was around to see planets forming and undergoing dramatic changes before settling in their present configuration. In order to understand what came before us — before life on Earth and before Earth itself — scientists need to hunt for clues to that mysterious distant past.

Those clues come in the form of asteroids, comets and other small objects. Like detectives sifting through forensic evidence, scientists carefully examine these small bodies for insights about our origins. They tell of a time when countless meteors and asteroids rained down on the planets, burned up in the Sun, shot out beyond the orbit of Neptune or collided with one another and shattered into smaller bodies. From distant, icy comets to the asteroid that ended the reign of the dinosaurs, each space rock contains clues to epic events that shaped the solar system as we know it today — including life on Earth.

NASA’s missions to study these “non-planets” help us understand how planets including Earth formed, locate hazards from incoming objects and think about the future of exploration. They have played key roles in our solar system’s history, and reflect how it continues to change today.

“They might not have giant volcanoes, global oceans or dust storms, but small worlds could answer big questions we have about the origins of our solar system,” said Lori Glaze, acting director for the Planetary Science Division at NASA Headquarters in Washington.

NASA has a long history of exploring small bodies, beginning with Galileo’s 1991 flyby of asteroid Gaspra. The first spacecraft to orbit an asteroid, Near Earth Asteroid Rendezvous (NEAR) Shoemaker, also successfully landed on asteroid Eros in 2000 and took measurements that originally hadn’t been planned. The Deep Impact mission drove a probe into Comet Tempel 1 in 2005 and prompted scientists to rethink where comets formed. More recent efforts have built on those successes and will continue to teach us more about our solar system. Here’s an overview of what we can learn:

Image above: This representation of Ceres’ Occator Crater in false colors shows differences in the surface composition. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Building Blocks of Planets

Our solar system as we know it today formed from grains of dust — tiny particles of rock, metal and ice — swirling in a disk around our infant Sun. Most of the material from this disk fell into the newborn star, but some bits avoided that fate and stuck together, growing into asteroids, comets and even planets. Lots of leftovers from that process have survived to this day. The growth of planets from smaller objects is one piece of our history that asteroids and comets can help us investigate.

“Asteroids, comets and other small bodies hold material from the solar system’s birth. If we want to know where we come from, we must study these objects,” Glaze said.

Two ancient fossils providing clues to this story are Vesta and Ceres, the largest bodies in the asteroid belt between Mars and Jupiter. NASA’s Dawn spacecraft, which recently ended its mission, orbited both of them and showed definitively that they are not part of the regular “asteroid club.” While many asteroids are loose collections of rubble, the interiors of Vesta and Ceres are layered, with the densest material at their cores. (In scientific terms, their interiors are said to be “differentiated.”) This indicates both of these bodies were on their way to becoming planets, but their growth was stunted — they never had enough material to get as big as the major planets.

But while Vesta is largely dry, Ceres is wet. It may have as much as 25 percent water, mostly bound up in minerals or ice, with the possibility of underground liquid. The presence of ammonia at Ceres is also interesting, because it typically requires cooler temperatures than Ceres’ current location. This indicates the dwarf planet could have formed beyond Jupiter and migrated in, or at least incorporated materials that originated farther from the Sun. The mystery of Ceres’ origins shows how complex planetary formation can be, and it underscores the complicated history of our solar system.

Image above: This artist’s concept depicts the spacecraft of NASA’s Psyche mission near the mission’s target, the metal asteroid Psyche. Image Credits: NASA/JPL-Caltech/Arizona State Univ./Space Systems Loral/Peter Rubin.

Although we can indirectly study the deep interiors of the planets for clues about their origins, as NASA’s InSight mission will do on Mars, it’s impossible to drill down into the core of any sizeable object in space, including Earth. Nevertheless, a rare object called Psyche may offer the opportunity to explore a planet-like body’s core without any digging. Asteroid Psyche appears to be the exposed iron-nickel core of a protoplanet — a small world that formed early in our solar system’s history but never reached planetary size. Like Vesta and Ceres, Psyche saw its path to planethood disrupted. NASA’s Psyche mission, launching in 2022, will help tell the story of planet formation by studying this metal object in detail.

Image above: Artist’s impression of NASA’s New Horizons spacecraft encountering 2014 MU69, a Kuiper Belt object that orbits the Sun 1 billion miles (1.6 billion kilometers) beyond Pluto, on Jan. 1, 2019. Image Credits: NASA/JHUAPL/SwRI.

Farther afield, NASA’s New Horizons spacecraft is currently on its way to a distant object called 2014 MU69, nicknamed “Ultima Thule” by the mission. One billion miles farther from the Sun than Pluto, MU69 is a resident of the Kuiper Belt, a region of ice-rich objects beyond the orbit of Neptune. Objects like MU69 may represent the most primitive, or unaltered, material that remains in the solar system. While the planets orbit in ellipses around the Sun, MU69 and many other Kuiper Belt objects have very circular orbits, suggesting they have not moved from their original paths in 4.5 billion years. These objects may represent the building blocks of Pluto and other distant icy worlds like it. New Horizons will make its closest approach to MU69 on Jan. 1, 2019 — the farthest planetary flyby in history.

“Ultima Thule is incredibly scientifically valuable for understanding the origin of our solar system and its planets,” said Alan Stern, principal investigator of New Horizons, based at Southwest Research Institute in Boulder, Colorado. “It’s ancient and pristine, and not like anything we’ve seen before.”

Delivery of the Elements of Life

Small worlds are also likely responsible for seeding Earth with the ingredients for life. Studying how much water they have is evidence for how they helped seed life on Earth.

“Small bodies are the game changers. They participate in the slow and steady evolution of our solar system over time, and influence planetary atmospheres and opportunities for life. Earth is part of that story,” said NASA’s chief scientist Jim Green.

Image above: This “super-resolution” view of asteroid Bennu was created using eight images obtained by NASA’s OSIRIS-REx spacecraft on Oct. 29, 2018, from a distance of about 205 miles (330 kilometers). Image Credits: NASA/Goddard/University of Arizona.

One example of an asteroid containing the building blocks of life is Bennu, the target of NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) mission. Bennu may be loaded with molecules of carbon and water, both of which are necessary for life as we know it. As Earth formed, and afterward, objects like Bennu rained down and delivered these materials to our planet. These objects did not have oceans themselves, but rather water molecules bound up in minerals. Up to 80 percent of Earth’s water is thought to have come from small bodies like Bennu. By studying Bennu, we can better understand the kinds of objects that allowed a barren young Earth to blossom with life.

Bennu likely originated in the main asteroid belt between Mars and Jupiter, and it’s thought to have survived a catastrophic collision that happened between 800 million and 2 billion years ago. Scientists think a big, carbon-rich asteroid shattered into thousands of pieces, and Bennu is one of the remnants. Rather than a solid object, Bennu is thought to be a “rubble pile” asteroid — a loose collection of rocks stuck together through gravity and another force scientists call “cohesion.” OSIRIS-REx, which will arrive at Bennu in early December 2018, after a 1.2-billion-mile (2-billion-kilometer) journey, and will bring back a sample of this intriguing object to Earth in a sample-return capsule in 2023.

The Japanese Hayabusa-2 mission is also looking at an asteroid from the same family of bodies thought to have delivered ingredients for life to Earth. Currently in orbit at asteroid Ryugu, with small hopping rovers on the surface, the mission will collect samples and return them in a capsule to Earth for analysis by the end of 2020. We will learn a lot comparing Bennu and Ryugu, and understanding the similarities and differences between their samples.

Tracers of Solar System Evolution

Most of the material that formed our solar system, including Earth, didn’t live to tell the tale. It fell into the Sun or was ejected beyond the reaches of our most powerful telescopes; only a small fraction formed the planets. But there are some renegade remnants of the early days when the stuff of planets swirled with an uncertain fate around the Sun.

A particularly catastrophic time for the solar system was between 50 and 500 million years after the Sun formed. Jupiter and Saturn, our system’s most massive giants, reorganized the objects around them as their gravity interacted with smaller worlds such as asteroids. Uranus and Neptune may have originated closer to the Sun and been kicked outward as Jupiter and Saturn moved around. Saturn, in fact, may have prevented Jupiter from “eating” some of the terrestrial planets, including Earth, as its gravity counteracted Jupiter’s further movement toward the Sun.

Image above: Conceptual image of the Lucy mission to the Trojan asteroids. Image Credits: NASA/SwRI.

Swarms of asteroids called the Trojans could help sort out the details of that turbulent period. The Trojans comprise two clusters of small bodies that share Jupiter’s orbit around the Sun, with one group ahead of Jupiter and one trailing behind. But some Trojans seem to be made of different materials than others, as indicated by their varying colors. Some are much redder than others and may have originated beyond the orbit of Neptune, while the grayer ones may have formed much closer to the Sun. The leading theory is that as Jupiter moved around long ago, these objects were corralled into Lagrange points — places where the gravity of Jupiter and the Sun create holding areas where asteroids can be captured. The Trojans’ diversity, scientists say, reflects Jupiter’s journey to its present location. “They’re the remnants of what was going on the last time Jupiter moved,” said Hal Levison, researcher at Southwest Research Institute.

NASA’s Lucy mission, launching in October 2021, will send a spacecraft to the Trojans for the first time, thoroughly investigating six Trojans (three asteroids in each swarm). For Levison, the mission’s principal investigator, the spacecraft will test ideas he and colleagues have been working on for decades about Jupiter’s reshaping of the solar system. “What would really be interesting is what we don’t expect,” he said.

Processes in an Evolving Solar System

After sundown, under the right conditions, you may notice scattered sunlight in the ecliptic plane, the region of the sky where the planets orbit. This is because sunlight is being scattered by dust left over from the collisions of small bodies such as comets and asteroids. Scientists call this phenomenon “zodiacal light,” and it’s an indication that our solar system is still active. Zodiacal dust around other stars indicates that they, too, may harbor active planetary systems.

Dust from small bodies has had an important role in our planet in particular. About 100 tons of meteoritic material and dust material fall on Earth every day. Some of it comes from comets, whose activity has direct implications for Earth’s evolution. As comets approach the Sun and experience its heat, gases inside the comet bubble up and carry away dusty material from the comet — including ingredients for life. NASA’s Stardust spacecraft flew by Comet 81P/Wild and found that cometary dust contains amino acids, which are building blocks of life.

Image above: This view shows Comet 67P/Churyumov-Gerasimenko as seen by the OSIRIS wide-angle camera on ESA’s Rosetta spacecraft on September 29, 2016, when Rosetta was at an altitude of 14 miles (23 kilometers). Image Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

Occasional outbursts of gas and dust observed in comets indicate activity on or near their surfaces, such as landslides. The European Space Agency’s Rosetta mission, which completed its exploration of Comet 67P/Churyumov-Gerasimenko in 2016, delivered unprecedented insights about cometary activity. Among the changes in the comet, the spacecraft observed a massive cliff collapse, a large crack get bigger and a boulder move. “We discovered that boulders the size of a large truck could be moved across the comet’s surface a distance as long as one-and-a-half football fields,” Ramy El-Maarry, a member of the U.S. Rosetta science team from the University of Colorado, Boulder, said in 2017.

Comets also influence planetary motion today. As Jupiter continues to fling comets outward, it moves inward ever so slightly because of the gravitational dance with the icy bodies. Neptune, meanwhile, throws comets inward and in turn gets a tiny outward push. Uranus and Saturn are also moving outward very slowly in this process.

“Right now we’re talking about teeny amounts of motions because there’s not a lot of mass left,” Levison said.

Fun fact: The spacecraft that has seen the most comets is NASA’s Solar & Heliospheric Observatory (SOHO), most famous for its study of the Sun. SOHO has seen the Sun “eat” thousands of comets, which means that these small worlds were spraying material in the inner part of the solar system on their journey to become the Sun’s dinner.

Image above: This animation portrays a comet as it approaches the inner solar system. Light from the Sun warms the comet’s core, or nucleus, an object so small it cannot be seen at this scale. Image Credits: NASA/JPL-Caltech.

Hazards to Earth

Asteroids can still pose an impact hazard to the planets, including our own.

While the Trojans are stuck being Jupiter groupies, Bennu, the target of the OSIRIS-REx mission, is one of the most potentially hazardous asteroids to Earth that is currently known, even though its odds of colliding with Earth are still relatively small; scientists estimate Bennu has a 1‐in‐2,700 chance of impacting our planet during one of its close approaches to Earth in the late 22nd century. Right now, scientists can predict Bennu’s path quite precisely through the year 2135, when the asteroid will make one of its close passes by Earth. Close observations by OSIRIS-REx will get an even tighter handle on Bennu’s journey, and help scientists working on safeguarding our planet against hazardous asteroids to better understand what it would take to deflect one on an impact trajectory.

“We’re developing a lot of technologies for operating with precision around these kinds of bodies, and targeting locations on their surfaces, as well as characterizing their overall physical and chemical properties. You would need this information if you wanted to design an asteroid deflection mission,” said Dante Lauretta, principal investigator for the OSIRIS-REx mission, based at the University of Arizona in Tucson.

Dart Moon Collision

Video above: This animation shows how NASA’s Double Asteroid Redirection Test (DART) would target and strike the smaller (left) element of the binary asteroid Didymos to demonstrate how a kinetic impact could potentially redirect an asteroid as part of the agency’s planetary defense program. Animation Credits: NASA/JHUAPL.

Another upcoming mission that will test a technique for defending the planet from naturally occurring impact hazards is NASA’s Double Asteroid Redirection Test (DART) mission, which will attempt to change a small asteroid’s motion. How? Kinetic impact — in other words, collide something with it, but in a more precise and controlled way than nature does it.

DART’s target is Didymos, a binary asteroid composed of two objects orbiting each other. The larger body is about half a mile (800 meters) across, with a small moonlet that is less than one-tenth of a mile (150 meters) wide. An asteroid this size could result in widespread regional damage if one were to impact Earth. DART will deliberately crash itself into the moonlet to slightly change the small object’s orbital speed. Telescopes on Earth will then measure this change in speed by observing the new period of time it takes the moonlet to complete an orbit around the main body, which is expected to be a change of less than a fraction of one percent. But even that small of change could be enough to make a predicted impactor miss Earth in some future impact scenario. The spacecraft, being built by the Johns Hopkins University Applied Physics Laboratory, is scheduled for launch in spring-summer 2021.

Didymos and Bennu are just two of the almost 19,000 known near-Earth asteroids. There are over 8,300 known near-Earth asteroids the size of the moonlet of Didymos and larger, but scientists estimate that about 25,000 asteroids in that size range exist in near-Earth space. The space telescope helping scientists discover and understand these kinds of objects, including potential hazards, is called NEOWISE (which stands for Near-Earth Object Wide-field Infrared Survey Explorer).

“For most asteroids, we know little about them except for their orbit and how bright they look. With NEOWISE, we can use the heat emitted from the objects to give us a better assessment of their sizes,” said Amy Mainzer, principal investigator of NEOWISE, based at NASA’s Jet Propulsion Laboratory. “That’s important because asteroid impacts can pack quite a punch, and the amount of energy depends strongly on the size of the object.”

Image above: This artist’s concept shows the Wide-field Infrared Survey Explorer, or WISE, spacecraft, in its orbit around Earth. In its NEOWISE mission it finds and characterizes asteroids. Image Credits: NASA/JPL-Caltech.

Small Worlds as Pit Stops, Resources for Future Exploration

There are no gas stations in space yet, but scientists and engineers are already starting to think about how asteroids could one day serve as refueling stations for spacecraft on the way to farther-flung destinations. These small worlds might also help astronauts restock their supplies. For example, Bennu likely has water bound in clay minerals, which could perhaps one day be harvested for hydrating thirsty space travelers.

“In addition to science, the future will indeed be mining,” Green said. “The materials in space will be used in space for further exploration.”

How did metals get on asteroids? As they formed, asteroids and other small worlds collected heavy elements forged billions of years ago. Iron and nickel found in asteroids were produced by previous generations of stars and incorporated in the formation of our solar system.

These small bodies also contain heavier metals forged in stellar explosions called supernovae. The violent death of a star, which can lead to the creation of a black hole, spreads elements heavier than hydrogen and helium throughout the universe. These include metals like gold, silver and platinum, as well as oxygen, carbon and other elements we need for survival. Another kind of cataclysm — the collision of supernova remnants called neutron stars — can also create and spread heavy metals. In this way small bodies are also forensic evidence of the explosions or collisions of long-dead stars.

Because of big things, we now have a lot of very small things. And from small things, we get big clues about our past — and possibly resources for our future. Exploring these objects is important, even if they aren’t planets.

They are small worlds, after all.

Related links:

Near Earth Asteroid Rendezvous (NEAR): https://solarsystem.nasa.gov/missions/near-shoemaker/in-depth/

Deep Impact mission: https://solarsystem.nasa.gov/missions/deep-impact-epoxi/in-depth/

NASA’s Dawn: https://dawn.jpl.nasa.gov/

NASA’s InSight: https://mars.nasa.gov/insight/

NASA’s Psyche: https://psyche.asu.edu/

NASA’s New Horizons: http://pluto.jhuapl.edu/

NASA’s OSIRIS-REx: http://www.asteroidmission.com/

NASA’s Lucy: https://solarsystem.nasa.gov/missions/lucy/in-depth/

NASA’s Double Asteroid Redirection Test (DART): http://dart.jhuapl.edu/

NASA’s NEOWISE: https://neowise.ipac.caltech.edu/

ESA’s  Rosetta: http://www.nasa.gov/rosetta/

JAXA’s Hayabusa-2: http://global.jaxa.jp/projects/sat/hayabusa2/

Images (mentioned), Animation (mentioned), Video (mentioned), Text, Credits: NASA/Tony Greicius/Elizabeth Landau.

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