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What Is The Lithosphere? – WorldAtlas – Worldatlas.com

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The lithosphere refers to the hard, rocky outermost layer of any terrestrial planet or natural satellite. On Planet Earth, the lithosphere is mainly made up of the crust and the solid outer portion of the upper mantle. One of the major spheres of the Earth, the lithosphere is primarily the terrestrial component comprising solid landmasses such as the continents and islands on which all biological life exists. The lithosphere is severely affected by human activities such as mining, deforestation, agriculture, overgrazing, and urbanization.

Why Is It Called Lithosphere?

A diagram showing the extent of the lithosphere on Earth.

The term lithosphere has been derived from the Greek words lithos, which means rocks or stones, and sphaeros, which means sphere. The lithosphere or rocksphere thus refers to the hard and rocky outer layer of the Earth, made up of the crust and the upper mantle. The lithosphere can extend up to a depth of over 100 km. Below the lithosphere lies the asthenosphere, which refers to the weaker, hotter, and much deeper portion of the upper mantle. The lithosphere remains hard for longer time periods and deforms elastically, whereas the asthenosphere deforms viscously. The lithosphere is, therefore, lesser ductile than the asthenosphere.

History Of The Lithosphere Concept

The concept of the lithosphere as a strong outer layer of the Earth was first put forward by the English mathematician Augustus Edward Hough Love in his 1911 monograph. The concept was further developed by the American geologist Joseph Barrell, who introduced the term lithosphere. The Canadian geologist Reginald Aldworth Daly strengthened these concepts even further. Love, Barrell, and Daly’s work are widely revered by the geophysicist and geologist communities, serving as the backbone of the theory of plate tectonics.

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Composition Of The Lithosphere

The composition of the lithosphere varies depending on whether it is located on land or under the oceans. It is known that the Earth’s crust is not homogeneous and is composed of different layers of rock, including sedimentary (at the top), metamorphic (at the middle), and basaltic rocks (at the bottom). Moreover, the lithosphere is broken into several large tectonic plates that move slowly but continuously at an average rate of about 10cm.

Types Of Lithosphere

There are mainly two types of lithosphere: oceanic and continental.

Oceanic Lithosphere

ocean lithosphere
The sea bed is part of the lithosphere.

Oceanic Lithosphere refers to the lithosphere associated with the oceanic crust that is present under the seas and oceans. The Oceanic lithosphere comprises the mafic crust and ultramafic mantle and tends to be comparatively denser than the continental lithosphere. Young oceanic lithosphere is usually found at the mid-ocean ridges, while the old oceanic lithosphere gets thickened as it ages and moves farther from the mid-oceanic ridge, getting recycled at the subduction zones.

This thickening of the oceanic lithosphere usually occurs by conductive cooling, where the hot asthenosphere is converted into a lithospheric mantle. It is to be noted that the oceanic lithosphere is comparatively younger than the continental lithosphere, and the oldest oceanic lithosphere is approximately 170 million years old.

Continental Lithosphere

lithosphere
Layer of soil and rock on the Earth’s crust forming the lithosphere.

Continental Lithosphere refers to the lithosphere associated with the continental crust. This lithosphere’s average thickness ranges between 40km to 280km. The continental lithosphere makes up about 40% of the Earth’s surface and 70% of the volume of the Earth’s crust. Scientists believe that the Earth originally had no continental crust, but ultimately the fractional differentiation of the oceanic crust led to the formation of the continental crust.

The Continental Lithosphere is, therefore, quite old than the oceanic lithosphere, and the oldest portions of the continental lithosphere are found underlying the cratons. However, due to its relatively low density, the continental lithosphere is not recycled at subduction zones, as it cannot subduct further than 100 km.

Subducted Lithosphere

Several 21st-century geophysical studies have revealed that there can be many large pieces of recycled lithospheric elements that have been subducted as far as 2900 km into the mantle. There is a strong belief that some pieces of the lithosphere can still float in the upper mantle and that some pieces can go down approximately 400 km while still being physically linked to continental plates further up the Earth’s surface.

Importance Of The Lithosphere

Lithosphere
Roots of plants growing in the lithosphere.

Being one of the major spheres of the Earth, the lithosphere aids greatly for life to flourish on the planet. The lithosphere’s uppermost portion that chemically interacts with the other three spheres is called the pedosphere. Besides being a rich source of minerals, the lithosphere provides our forests, grasslands, agricultural lands, and lands for human settlements. The movement of the tectonic plates is also responsible for the formation of mountains, volcanoes, and continents.

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Using atomic clocks in space to solve dark matter mystery – Innovation News Network

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A team of international scientists is proposing to send atomic clocks into space to detect and understand enigmatic dark matter.

Dark matter is a mystery that has plagued researchers for decades. This unknown essence represents 85% of all matter in the Universe, and although its effects can be observed, it has not been directly detected. Experts from the University of Delaware, the University of California, and the University of Tokyo are collaborating to solve this longstanding mystery by sending atomic clocks into space.

The research, ‘Direct detection of ultralight dark matter bound to the Sun with space quantum sensors,’ which is published in Nature Astronomy, plans to send two atomic clocks into the inner reaches of the solar system to search for ultralight dark matter that has wavelike properties that may affect the operation of the clocks.

What are atomic clocks?

Atomic clocks tell time by measuring the rapid oscillations of atoms and are already utilised in space to enable the Global Positioning System (GPS). In the future, space clocks could help navigate spacecraft and provide links to Earth-based cocks.

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All clocks mark time by using some form of a repetitive process, such as a swinging pendulum. However, atomic clocks use laser technology to manipulate and measure the oscillations of atoms which are extremely fast. For example, a clock based on strontium atoms ticks 430 trillion times per second, and atomic clocks are exceedingly more precise than any mechanical devices.

Historically, atomic clocks can cover the size of a couple of tables, but recent advances in precision and portability mean that some atomic clocks can now fit into a van, with NASA’s Deep Space Atomic Clock being even smaller, at around the size of a toaster.

Nevertheless, different types of clocks, based on much higher frequencies, have been developed over the last 15 years, such as optical clocks that are orders of magnitude more precise and will not lose even a second of time over billions of years.

Marianna Safronova, a physicist at the University of Delaware, said: “We now have portable clocks, and it’s fun to think about how you would go about sending such high-precision clocks to space and establish what great things we can do.

“It is a beautiful synergy between a quantum expert and particle theorists, and we are working on new ideas at the intersection of these two fields.”

Unravelling the mysterious properties of dark matter

The proposed research would send space clocks closer to the Sun than Mercury – an area they believe there is more dark matter to detect. These include atomic, nuclear, and molecular clocks that are currently being developed and are otherwise known as quantum sensors.

Safronova explained: “This was inspired by the Parker Solar Probe, the ongoing NASA mission that sent a spacecraft closer to the Sun than any other spacecraft has gone before. It has nothing to do with quantum sensors or clocks, but it showed that you could send a satellite very close to the Sun, sensing new conditions and making discoveries. That is much closer to the Sun than what we are proposing here.”

The aim of the study is to investigate ultralight dark matter, which the researchers believe could make a huge halo-like region that is bound to the Sun. Ultralight dark matter could cause the energies of atoms to oscillate, which will change how the clock ticks, although this effect depends on the atoms the clock uses. The researchers then monitor the differences in the clocks to look for dark matter.

“It has very specific properties and is a very specific dark matter that is detectable by clocks. What is observable is the ratio of those two clock frequencies. That ratio should oscillate if such dark matter exists,” Safronova said.

She explained that nuclear clocks, which are based on nuclear energy levels rather than atomic energy levels, may be the best clock for this research. She is currently involved in a project to build a prototype funded by the European Research Council.

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Space Atomic Clocks Could Unravel the Nature of Dark Matter – AZoQuantum

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Analyzing an atomic clock onboard a spacecraft within the orbit of Mercury and very close to the Sun could be the trick to revealing the nature of dark matter according to a new research article published in the December 5th issue of the journal Nature Astronomy.

Artist’s impression of a space atomic clock used to uncover dark matter. Image Credit: Kavli IPMU.

Dark matter composes over 80% of the mass in the universe, but it has thus far dodged detection on Earth, regardless of decades of experimental endeavors. A core component of these hunts is a hypothesis regarding the local density of dark matter, which establishes the number of dark matter particles moving via the detector at all times and thus the experimental sensitivity.

In a few models, this density can be a lot higher than is typically supposed, and dark matter can become more intense in certain regions than in others.

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One vital group of experimental searches is those using nuclei or atoms because these have realized extraordinary sensitivity to signals of dark matter. This is conceivable, in part, because when dark matter particles have extremely small masses, they prompt oscillations in the very constants of nature.

These oscillations, for example the interaction strength of the electromagnetic force or in the mass of the electron, alter the transition energies of nuclei and atoms in foreseeable ways.

An international group of scientists, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Project Researcher Joshua Eby, University of California, Irvine, Postdoctoral Fellow Yu-Dai Tsai, and University of Delaware Professor Marianna S. Safronova, recognized the potential in these oscillating signals.

They stated that in a specific region of the Solar System, between the orbit of Mercury and the Sun, the dark matter’s density could be exceptionally large, which would mean extraordinary sensitivity to the oscillating signals.

These signals could be captured by atomic clocks, which work by meticulously measuring the frequency of photons discharged in transitions of various states in atoms. Ultralight dark matter in the region of the clock experiment could alter those frequencies as the oscillations of the dark matter marginally increase and decrease the photon energy.

The more dark matter there is around the experiment, the larger these oscillations are, so the local density of dark matter matters a lot when analyzing the signal.

Joshua Eby, Project Researcher, Kavli Institute for the Physics and Mathematics of the Universe

While the accurate density of the dark matter near the Sun is not established, the scientists debate that even a comparatively low-sensitivity search could deliver crucial information.

The density of dark matter is just constrained in the Solar System by information concerning planet orbits. In the region between the Sun and Mercury, the planet closest to the Sun, there is nearly no constraint. Therefore, a measurement onboard a spacecraft could rapidly expose world-leading restrictions on dark matter in these models.

The technology to test their theory is already present. Eby says the NASA Parker Solar Probe, which has been functioning since 2018 with the help of shielding, has moved closer to the Sun than any manmade craft in history and is at present working within the orbit of Mercury, with plans to travel even closer to the Sun in a year.

Atomic clocks in space are already established for numerous reasons other than hunting for dark matter.

Long-distance space missions, including possible future missions to Mars, will require exceptional timekeeping as would be provided by atomic clocks in space. A possible future mission, with shielding and trajectory very similar to the Parker Solar Probe, but carrying an atomic clock apparatus, could be sufficient to carry out the search.

Joshua Eby, Project Researcher, Kavli Institute for the Physics and Mathematics of the Universe

More from AZoQuantum: Precise Atomic Clock Proves Einstein was Right on Time

Journal Reference

Tsai, Y-D., et al. (2022) Direct detection of ultralight dark matter bound to the Sun with space quantum sensors. Nature Astronomy. doi.org/10.1038/s41550-022-01833-6.

Source:  https://www.ipmu.jp/en

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After lunar flyby, NASA’s Orion spacecraft is set to splashdown on Sunday – Ars Technica

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Enlarge / Orion, the Moon, and a crescent Earth on Monday.
NASA

The Orion spacecraft swung by the Moon on Monday, flying to within 130 km of that world’s surface as it set course for a return to Earth this weekend.

In making this “powered flyby burn” to move away from the Moon, Orion’s service module performed its longest main engine firing to date, lasting 3 minutes and 27 seconds. After successful completion of the maneuver, NASA’s mission management team gave the “go” to send recovery teams out into the Pacific Ocean, where Orion is due to splashdown on Sunday, during the middle of the day.

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By getting into an orbit around the Moon, and back out of it again during its deep space mission, Orion has now completed four main propulsive burns. This completes a big test of the spacecraft and its propulsive service module, which was built by the European Space Agency. Although a boilerplate version of Orion made a flight in 2014, it did so without a service module.

As part of this Artemis I mission, NASA is now three weeks into a 25.5-day test flight of the Orion spacecraft. The goal is to validate the spacecraft’s capabilities ahead of a human flight of the vehicle in about two years’ time, the Artemis II mission.

Orion has met most of its main objectives to date, with only the entry, descent, and splashdown part of its mission ahead of it. The spacecraft’s heat shield must demonstrate its ability to survive reentry at a velocity of 39,400 kph. This big test will come Sunday during a fiery reentry into Earth’s atmosphere.

A minor power issue

So far, Orion’s test flight has gone remarkably well. Typically, with new spacecraft, there are issues with thrusters, navigation, or onboard avionics and more. However, Orion has had no major issues. The only real troubleshooting has involved a problem with power systems on the vehicle.

The issue has occurred with four “latching current limiters” that help route power to propulsion and heating systems on Orion. For some reason, automated controllers on Orion commanded the four current limiters to “open” when no such command was supposed to be sent. “We’re not exactly sure on the root cause of the problem, but teams are doing tests on the ground,” said Debbie Korth, the Orion Program deputy manager, during a briefing on Monday evening at Johnson Space Center in Houston.

Overall, the Orion spacecraft has performed like a champion.
Enlarge / Overall, the Orion spacecraft has performed like a champion.
NASA

This system is somewhat like a circuit breaker box in a home, and for some reason four of the breakers were opened when they were not supposed to be. This did not pose a threat to Orion, as there are backup power systems. Had a crew been on board it would have required a minor procedure to account for the problem.

In an interview after the news briefing, Korth said she did not think the glitch would have an impact on the service module that will be used for the Artemis II mission. This hardware is already built and being tested in the United States.

“I think it’s probably too early to say for sure, but ideally we will not want to perturb the Artemis II service module,” she said. “This may very well be something we can handle with software.”

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