Moon rocks, asteroid impacts miscalculation?


This video says about itself:

Astronomy – Ch. 8: Origin of the Solar System (16 of 19) Late Heavy Bombardment

21 March 2015

In this video I will explain how astronomers deduced that early Solar System was a very violent place.

The video shows most scientists’ views of a year ago.

However, now …

From Science News:

Moon rocks may have misled asteroid bombardment dating

Spike in impacts 3.9 billion years ago may be mathematical mirage, study finds

By Laurel Hamers

3:00pm, September 12, 2016

A barrage of rocks hitting the solar system 3.9 billion years ago could have dramatically reshaped Earth’s geology and atmosphere. But some of the evidence for this proposed bombardment might be shakier than previously believed, new research suggests. Simplifications made when dating moon rocks could make it appear that asteroid and comet impacts spiked around this time even if the collision rate was actually decreasing, scientists report the week of September 12 in the Proceedings of the National Academies of Sciences.

Many scientists think that a period of relative calm after Earth formed 4.6 billion years ago was interrupted by a period called the Late Heavy Bombardment, when rocky debris pummeled Earth and the other planets. The moon’s cratered surface holds the best evidence for this event; scientists have measured radioactive decay of argon gas trapped inside moon rocks to date when craters on the moon were formed.

Many of the hundreds of moon rocks analyzed appear to be around 3.9 billion years old. That suggests the number of rocks hitting the moon suddenly spiked at that time — evidence for a Late Heavy Bombardment.

Geochemists Patrick Boehnke and Mark Harrison of UCLA took a second look at the data. Measuring argon from the same rock at different temperatures leeches the gas from different parts of the rock’s crystals; if all those age values align, researchers can be relatively confident they’re getting an accurate age. But many of the lunar samples previously analyzed gave different ages depending on the temperature at which their argon content was measured.

Instead of colliding sharply once and sitting undisrupted, which might give more uniform age data at different temperatures, these lunar rocks were probably tossed around and slammed into other rocks many times, Boehnke says. So assigning one impact age to those rocks might be an oversimplification.

Boehnke and Harrison created a model to simulate how this simplification might affect the patterns seen when scientists looked at the ages of many rocks. The team modeled 1,000 rocks and assigned each one an impact age. Some rocks hadn’t been knocked around and had a clear impact age. Others had been smashed repeatedly, which changed their argon content and obscured the actual impact age assigned by the model.

The model assumed that asteroid collisions decreased over time — that more of the rocks were older and fewer were newer. But still, collision ages appeared to spike 3.9 billion years ago thanks to the fuzziness introduced by the disrupted rocks. So the apparent asteroid increase at that time might just be a quirk due to the way the argon dating data were compiled and analyzed, not an indication of something dramatic actually happening.

“We can’t say the Late Heavy Bombardment didn’t happen,” Boehnke says. Nor do the results invalidate the technique of argon dating, which is used widely by geologists. Instead, Boehnke says, it points to the need for more nuanced interpretation of lunar rock data.

“A lot of data that shows this complexity is being interpreted in a very simplistic way,” he says.

Planetary scientist Simone Marchi says he finds the paper “certainly convincing in saying that we have to be very careful” when interpreting argon dating data from lunar samples.

But there’s other evidence for a Late Heavy Bombardment that doesn’t rely on argon dating, such as dating from more stable radioactive elements and analysis of overlapping craters on the moon, says Marchi, of the Southwest Research Institute in Boulder, Colo. He supports the idea of a gentler Late Heavy Bombardment 4.1 billion years ago, instead of a dramatic burst 3.9 billion years ago (SN: 8/23/14, p.13).

Other recent work has also pointed out limitations in argon dating, says Noah Petro, a planetary geologist at NASA Goddard Space Flight Center in Greenbelt, Md., who wasn’t part of the study.   Collecting new samples and analyzing old ones with newer techniques could help scientists update their view of the early solar system. “We’re at this point with the moon right now where we’re finding the limitations of what we think we know.”

Where the young hot Earth cached its gold. New view offers alternative history of how precious metals sank into the planet’s core: here.

Cave diving in the Bahamas, videos


This video from the USA says about itself:

10 August 2016

This is the trailer for the giant screen film ANCIENT CAVES that is being shown at the Giant Screen Cinema Association (GSCA) conference in Toronto, October 2016. The trailer is in 4:3 aspect ratio as this is an OMNIMAX format dome original which will obviously look a little distorted and strangely composed on a small flat screen.

ANCIENT CAVES is the first giant screen film to be produced exclusively for OMNIMAX theaters in over 30 years.

Come to the GSCA conference and see this in IMAX!

Transcript:

Deep below the surface of the Bahamian island of Abaco, lies a secret cave few humans have ever visited. The journey here is dark and treacherous, but the cave contains valuable secrets of the Earth’s ancient climate. They are hidden in these formations, made of the purest calcite crystal. They were created by dripping water during an ice age, when sea levels were hundreds of feet lower and this cave was dry.

Brian Kakuk is a world-renowned cave explorer. Today he is on a mission to recover a stalagmite sample from deep inside the cave.

Scientists can analyze these crystal formations to unlock a valuable history of climate going back hundred of thousands of years.

Sixteen hundred miles away, at the University of Minnesota, cave paleoclimatologist Dr. Gina Moseley removes a sample from a stalagmite.

DR MOSELEY: Through looking at these deposits I get information about how the climate has changed in the past, how the sea level has changed in the past, and also how the landscape has evolved above the cave.

Dr. Moseley works with Dr. Larry Edwards, the world’s foremost expert in dating cave samples.

DR. EDWARDS: It turns out that one of the huge advantages of cave deposits is that you can date them really, really well.”

DR. MOSELEY: Oh Wow!

JOHN ACKERMAN: It’s incredible!

Doctor Edwards and Doctor Mosley began their work together exploring the Earth’s ancient climate in this dry cave in Minnesota.

JOHN ACKERMAN: Oh Gina, come take a look at this, would this be a good specimen?

DR. MOSELEY: That’s perfect. It’s already broken and it looks like a nice long record in there.

But as they gathered data from caves elsewhere around the globe, there were new questions about what causes the great fluctuations in the Earth’s temperature that lead to ice ages, droughts, and sea level change.

The answers require samples from some of the most difficult and dangerous places on Earth.

Ancient Caves is a giant screen film that follows expeditions to some of the world’s most astonishing caves in search of clues about our changing planet. The film takes viewers to the Nevada desert, the Yucatan in Mexico, and the deep, stunningly beautiful and treacherous Crystal Cave in the Bahamas.

DR. MOSELEY: I love the journey you go in, in a cave. You never know what’s around the next corner.”

Ancient Caves is the first giant screen film in more than 30 years to be shot and produced specifically for the OMNIMAX format.

Shot with a combination of traditional 15/70 and high-tech ultra-high resolution digital cameras, our film crew can go where traditional cameras cannot.

Ancient Caves is a science adventure film and a story of exploration. The underwater sequences will be shot in the most beautiful and dangerous caves in the world.

DR. MOSELEY: Anything below the current sea level is hard for us to get to so we’re reliant on diving experts basically to collect the samples for us and it’s dangerous work and as a result of that there has been limited work done below sea level.”

Caves offer an incredible environment for OMNIMAX because there is something to see in all directions–even straight up. It’s perfect for the immersion experience that only these theaters can provide.

This video from the USA says about itself:

12 August 2016

During the first shoot for our IMAX film ANCIENT CAVES, Cameraman Todd from the Blue World team was wearing a 3D GoPro rig on his helmet. This is a short video extra of 3D “behind the scenes” footage from that shoot with some narration from Todd. This is a wonderful way to get the feel for what it’s like to go cave diving if you have some 3D glasses or a 3D adapter for your phone!!

Jonathan Bird’s Blue World is an Emmy Award-winning underwater science/adventure program that airs on public television in the United States.

Saturn’s moon Enceladus, new study


This video says about itself:

Warm Water Spots Found On Saturn’s Icy Moon Enceladus

12 March 2015

Astronomers have detected the first active hydrothermal vents outside of Earth’s seafloor on Saturn’s icy moon Enceladus, indicating conditions that could be hospitable to the initial development of life.

New research suggests the existence of warm spots on the ocean floor of Saturn’s icy moon Enceladus.

They could be the first active hydrothermal vents to be detected outside of Earth’s seafloor, and their conditions may even be similarly hospitable to the initial development of life.

Two studies, one led by the University of Colorado, Boulder and the other by the Southwest Research Institute in Texas, support the possible existence of this hydrothermal activity.

In 2005, the Cassini orbiter captured images of geysers shooting out of the moon’s surface, which led to the discovery of an underground sea believed to be approximately 6 miles deep and under about 25 miles of icy crust.

Scientists discovered particles from the geysers in one of Saturn’s rings and using an instrument onboard Cassini were able to analyze the tiny, uniform dust particles. They found they were rich in silica which is common on Earth but different from the usual ice crystals found in Saturn’s E-ring.

Because silica has such well-known properties, the only way they could create similar particles in the lab was using slightly alkaline, low-in-salinity water at temperatures of at least 194 degrees Fahrenheit.

Despite the ultra-cold environment, the moon’s high core temperature is thought to come from an effect called tidal heating where Saturn’s gravitational pull on the moon generates heat.

From the International Business Times:

On Saturn’s Moon Enceladus, Water Vapor Erupts In Giant Curtains: Study

By Avaneesh Pandey

May 08 2015 8:35 AM EDT

In 2005, NASA’s Cassini-Huygens spacecraft found evidence of an icy spray issuing from the southern polar region of Saturn’s sixth-largest moon, Enceladus. Now, just two months after scientists confirmed the presence of hydrothermal activity on the moon, researchers have claimed that the eruption of water vapor on its surface might be in the form of broad, curtain-like sheets, rather than discrete jets.

“We think most of the observed activity represents curtain eruptions from the ‘tiger stripe’ fractures, rather than intermittent geysers along them,” Joseph Spitale, a Cassini mission participating scientist and senior scientist at the Planetary Science Institute in Tucson, Arizona, said, in a statement, referring to prominent wavy fractures along the moon’s surface. “Some prominent jets likely are what they appear to be, but most of the activity seen in the images can be explained without discrete jets.”

According to a study published Thursday in the journal Nature, these “phantom jets” seen in simulated images produced by scientists line up perfectly with some of the features seen in real Cassini images. This means that the discrete geysers that scientists have observed on Enceladus are, in fact, an optical illusion created in places where these curtains fold against one another. This illusion is also responsible for creating regions of phantom brightness when viewers are looking through the folds of watery curtains.

“The viewing direction plays an important role in where the phantom jets appear,” Spitale said, in the statement. “If you rotate your perspective around Enceladus’ South Pole, such jets would seem to appear and disappear.”

On Earth, these curtain eruptions occur in regions of volcanic activity such as Hawaii, Iceland and the Galapagos Islands. However, unlike Enceladus’ watery curtains, these are curtains of fire.

Enceladus is believed to be covered with a layer of ice about 19 miles to 25 miles thick. Evidence strongly suggests that the moon harbors a six-mile-deep ocean, with temperatures reaching up to 194 degrees Fahrenheit below its thick, icy surface, making it a prime location to look for extraterrestrial life.

Bahamas, built by bacteria from Saharan dust?


This video says about itself:

Wildlife of Exuma Island, Bahamas – Lonely Planet travel video

Visitors to sparsely populated Exuma, a remote island in the Bahamas, can expect a close encounter with sharks and iguanas.

From New Scientist:

Bahamian paradise built by bacteria using Saharan dust

13:40 28 July 2014 by Flora Graham

The Bahamas may have been created by bacteria thriving on minerals in dust from the Sahara desert, 8000 kilometres away.

In this NASA satellite image from 2009, it is possible to see how the many islands of the Bahamas are actually the highest points of distinct areas where the sea is shallow and turquoise.

These turquoise waters mark the top of the Bahama Banks – underwater columns of coral reef limestone more than 4500 metres tall that have formed over the past 100 million years. It was thought that tiny plants and animals generate the vast amounts of carbonate that make up the towers, similar to how coral reefs are formed. But the surrounding sea is poor in nutrients, so what would have sustained them is a mystery.

Now researchers including Peter Swart from the University of Miami’s Rosenstiel School of Marine and Atmospheric Science in Florida are showing that photosynthetic cyanobacteria may actually have done much of the construction.

Cyanobacteria are involved in the precipitation of calcium carbonate in the sea, but they would have needed an enormous amount of iron to do their work. This could have been provided by the dust that blows across the Atlantic from the Sahara.

There are characteristic traces of iron and manganese in recent carbonate sediment on the banks, pointing to their Saharan origin. So the team suggests that the Bahama Banks are being built up by cyanobacteria and may also have been in the past.

The results of this research are here.

Prehistoric meteor shower and evolution of life discovery


This video is called Late Ordovician Mass Extinction (Ordovician – Silurian).

From daily The Independent in Britain:

Scientists discover fragment of ‘missing link’ asteroid that led to explosion of life on Earth

James Vincent

Thursday 03 July 2014

Scientists in Sweden have discovered a never-before seen class of meteorite that could be the ‘missing link’ between a gigantic collision in the asteroid belt 470 million years ago and the subsequent explosion of diverse life forms here on Earth.

Although it’s usually thought that meteorite impacts are disastrous for species on Earth (the classic example is the colossal impact thought to have killed off the dinosaurs 66 million years ago) there’s plenty of evidence to suggest that these events can also be beneficial to the overall diversity on the planet.

It’s thought that just such an impact – or rather, a string of them – dramatically boosted biodiversity on the planet during the Ordovician Period some 470 million years ago. It’s believed that a collision of two asteroids (or possibly an asteroid and a comet) out in space caused a shower of meteors to rain down on Earth.

Over time fragments of this meteor shower have been found around the planet and dated to 470 million years ago – but until now scientists had not found any evidence of the ‘killer’ asteroid that started this chain of events.

During the Ordovician Period most life on Earth was found in the ocean, with jawless fish, molluscs and insect-like arthropods making up the bulk of the species roll-call. However, a study from 2008 showed that the planet went through a “major phase of biodiversification” at this time shortly after “the largest documented asteroid breakup event during the past few billion years”.

The evidence for this breakup comes from the abundance of L-chondrite meteorites – the second most common meteorite type – fragments of which first started appearing on Earth around 470 million years ago.

“Something we didn’t really know about before was flying around and crashed into the L-chondrites,” said Gary Huss, co-author of the study that analysed the sample (published in Earth and Planetary Science Letters). This newly-discovered fragment is thought to be that very object – the mysterious ‘bullet’.

The composition of the fragment differs from known meteorite samples and its exposure age – the length of time it sailed through space – places it at the ‘scene of the crime’ when meteors rained down on the planet during the Ordovician Period.

“It’s a very, very strange and unusual find,” Birger Schmitz, the lead author of the study, told Live Science. “I think [it] adds to the understanding that the meteorites that come down on Earth today may not be entirely representative of what is out there.”

It’s not clear exactly why the Ordovician meteor shower led to a greater variety of life on the plane although some more far-fetched theories suggest that life itself was ‘seeded’ by organisms hitching a ride on asteroids.

A more likely explanation is that the impact craters caused by the collisions provided perfect test-beds for developing life. When meteorites hit the surface of the planet they scooped out bubbling pools of minerals and nutrients that served – in Carl Zimmer’s words – as “natural beakers that synthesized new chemicals essential for life”. However, even this is still just a theory – and the impacts might have also fostered life by creating new habitats, like restructured shorelines.

If further geochemical tests on the newly discovered fragment confirm its suspected origins then scientists will have pinned down another piece of the solar system’s history – but figuring out what happened closer to home might be more difficult still.

Galapagos islands, evolution and sea levels


This video says about itself:

How Have Sea-Levels Influenced Evolution on the Galapagos Islands?

This movie is a simple 0 m to -210 m geographical loop sequence at 5 m increments. Important features are the substantial gaps between Galapagos’ “core” islands even at -100 m. However, below c. -130 m the various islands begin coalescing.

Research: “Exploring the combined role of eustasy and oceanic island thermal subsidence in shaping biodiversity on the Galápagos” by Jason R. Ali and Jonathan C. Aitchison from the Journal of Biogeography.

From Wiley Research News:

The Galapagos Islands have an iconic status in the history of evolutionary study, now new research shows that the islands’ own geological past may have influenced the evolution of the chain’s native species.

Writing in the Journal of Biogeography, Jason Ali and Jonathan Aitchison explore how fluctuating sea level changes over thousands of years impacted the island chain’s ecology. They estimate that when the sea retreated, most recently 20,000 years ago, the water would have been 144m below its current level.

As a result, Santa Cruz, the island in the center of the archipelago, would have expanded, enveloping many of the smaller islands, while creating a series of shallow ‘land bridges’ between the volcanic outcroppings. Such bridges explain the range and diversity of the islands’ species, such as snakes, geckos and iguanas, which appear landlocked to modern eyes.

“As soon as I saw that that half the islands in the archipelago were sat on a single, shallow, submarine platform, I realized that the implications for biology could be significant,” said Dr. Ali. “My geological knowledge told me that sea-level falls must have regularly re-connected the islands, and that this must have profoundly shaped the landlocked biota’s distribution, and very likely its composition.”

Ecuador has declared an emergency in the Galapagos Islands, saying that a cargo ship which ran aground last week still poses a threat to the archipelago’s fragile ecosystem: here. See also here.

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