The history of dust, through space and time

What is dust?

It's ridiculous to ask this question in India. Dust is everywhere. On the roads, in the nose, in the lungs. You lock your house, go on vacation for a month, you come back and you will notice a beautiful patina on the table. It's inside your laptop, which drives the fan nuts.

It is also in the atmosphere, orbiting the Earth, even in the space. It is nightmarish storms on Mars. Philip Pullman and Steven Erikson have written fantasy books about him. Dust is ubiquitous. (The only dust-free places I've seen are the photos stored on the Internet.)

But what exactly is it and where does all this come from?

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Earth

Dust is a fine particulate matter. It comes from a wide variety of sources. Atmospheric dust – or wind – that we know so much is composed of small particles sheared on solid objects. For example, rapidly blowing winds sweep particles of loose, dry soil into the air, giving rise to what is called fugitive dust. Another source is the smoke from the exhaust pipes.

Mites of the pyroglyphid family are another. They eat skin flakes, including those excreted by humans, and digest them with enzymes that remain in their poop. In your home, exposure to their poop (considered a form of dust) can trigger asthma attacks.

Winds lift particles off the surface of the Earth and transport them to the troposphere. Once the dust rises, it acts as an aerosol. It retains heat and warms the surface of the Earth. Once it is collected in sufficient quantities, it begins to affect the weather conditions of the regions below, including precipitation patterns.

Dust particles smaller than 10 microns penetrate your lungs and affect your respiratory health. They conspire with other pollutants and, taking advantage of the slow winds, stagnate in the National Capital Region of India during the winter. Particles smaller than 2.5 microns "increase the risk of mortality by age" (source) and significantly increase the number of hospital admissions.

There is also dust that travels thousands of kilometers to reach the most remote parts of the world. The Sahara is the largest source of desert dust in the world, according to a study. In June of this year, the tropical region of the Atlantic Ocean experienced its most dusty period in 15 years, with a huge wave that devastated north-eastern Chad to the center of the Americas. According to NASA's Earth Observatory, Saharan dust "is helping to build beaches in the Caribbean and fertilize soils in the Amazon."

This is not a task on your screen this morning # GOESEast captured a view of the Earth on the major Saharan disk #dust blowing across the Atlantic. https://t.co/P1F11zXUHI pic.twitter.com/JzwebkGibx

– NOAA satellites (@NOAASatellites) June 27, 2018

But speaking of dust that migrates over great distances, the transatlantic plume seems much less a journey than the dust brought to Earth by meteorites that have traveled hundreds of thousands of kilometers in space. When these rocks move towards the ground, the atmosphere burns dust in the form of dust and lets them hang in the upper atmosphere.

The atoms released by these particles into the mesosphere penetrate the planet's circulation system, moving from pole to pole over many months. They interact with other particles to leave a trail of charged particles. Scientists then use a radar to track these particles and learn more about the circulation itself. Some extraterrestrial dust particles also reach the surface of the Earth over time. They could carry imprints of physical and chemical reactions that they could have lived in space, even for billions of years.

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Orbit

In the mid-twentieth century, researchers used optical data and mathematical arguments to determine that about four million tonnes of meteoric dust hit our planet's atmosphere each year. This situation is alarming: the figure suggests that the number of meteorites in the space is much higher than expected. In turn, the threat to our satellites could have been underestimated. More careful assessments subsequently lowered the figure. A 2013 report indicates that 10 to 40 tons of meteoric dust enter the Earth's atmosphere each day.

Yet this figure is not low – and its effects are exacerbated by debris that humans themselves orbit around the Earth. The Wikipedia article on "Space Debris" carefully notes: "As of … July 2016, the US Strategic Command has detected a total of 17,852 artifacts in orbit over the Earth, of which 1,419 operational satellites. "But one line later, the number of objects less than 1 cm explodes to 170 million.

If a grain of dust of 0.00001 kg, carried by a breeze of 1.4 m / s, hits your face, you will not feel anything. Indeed, its momentum – the product of its mass and its speed – is very weak. But when a particle weighing one hundredth of a gram hits a satellite at a relative speed of 1.5 km / s, its speed is a thousand times higher. Suddenly, it is able to damage critical components and fine study surfaces, ending millions of dollars in multi-year missions in seconds. One study suggests that such particles, if they travel fast enough, can also generate tiny shock waves.

Before our next stop on Dust Travel, let's take a break in science fiction. The mid-century overestimation of the flow of meteoric dust may have prompted Arthur C. Clarke to write his 1961 novel, A moonlit fall. In history, a cruise ship called the Selene takes tourists over a basin of ultrafine dust, apparently of meteoric origin. But one day, a natural disaster causes the Selene sinking into the dust and trapping passengers in life-threatening conditions. After much desperation, a rescue mission is organized when an astronomer spots a heat trail pointing to Selene's location from space, aboard a spaceship called Lagrange II.

This name is a reference to the famous Lagrange points. As the Earth rotates around the Sun and the Moon turns around the Earth, their combined gravitational fields give rise to five points in the space where the force acting on an object is perfectly suited to maintaining its relative position. to the Earth and the Sun. These are called L1, L2, L3, L4 and L5.

The Indian Space Research Organization (ISRO) plans to launch its Aditya satellite, intended for the study of the Sun, bound for the N1. This is useful because in L1, the vision of the Sun Aditya will not be blocked by the Earth. However, objects in L1, L2 and L3 have an unstable equilibrium. Without maintenance measures from time to time, they tend to disengage from their positions.

But this is not the case with L4 and L5, objects for which the equilibrium remains more stable. And like everything that's been hanging around for a while, they're picking up dust.

In the 1950s, Polish astronomer Kazimierz Kordylewski claimed to have seen two clouds of dust at L4 and L5. These nebulous collections of particles have since been called Kordylewski clouds. Other astronomers, however, have disputed their existence. For example, the Hiten satellite did not find any significant dust concentrations in the L4 and L5 regions in 2009. Some argued that Hiten might have missed them because the dust clouds are too scattered.

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Space

Just two weeks ago, Hungarian astronomers claimed to have confirmed the presence of dust clouds in these regions (their papers here and here). Given that L4 and L5 are of interest for future space missions, astronomers will now need to validate this result and, if appropriate, assess the corresponding dust density and threat probabilities.

Unlike Kordylewski, who photographed at the top of a mountain, the Hungarian group relies on the ability of dust to polarize light. Light is electromagnetic radiation. Each light wave consists of an electric field and a magnetic field oscillating perpendicularly. Imagine different waves of light approaching the dust, their electric fields directed in arbitrary directions. However, after striking the dust, the particles polarize the waves, causing all the electric fields to align with a particular orientation.

When astronomers detect such light, they know that it has encountered dust in its path. With the help of different instruments and analytical techniques, they can then map the distribution of dust in the space through which light passes.

For example, the Planck telescope of the European Space Agency was able to draw up a picture of the dust around the Milky Way.

It's billions and billions of tons. Are your complaints about dust around the house not pale in comparison?

And even on this scale, it was a nuisance. We do not know if the galaxy is complaining but Brian Keating certainly did.

In March 2014, Keating and his team at Harvard University's Center for Astronomy announced they had discovered signs of increasing the volume of the universe by 10 times.⁸⁰ in just 10^-33 seconds a moment after his birth in the Big Bang. About 380,000 years later, the Big Bang's radiation remnants – known as the Cosmic Microwave Background (CMB) – were created. Keating et al used the BICEP2 detector at the South Pole to find cosmic inflation footprints on the CMB. The smoking gun: light of a certain wavelength polarized by the gravitational waves of the beginning of the universe.

Although the announcement was made with great fanfare – like "discovering the decade" and so on, their complaint soon became suspicious. Data from the Planck telescope and other observatories quickly showed that what Keating's team had discovered was actually light polarized by galactic dust. Just like that, their ambition to win a Nobel Prize has collapsed. Ashes to ashes, dust to dust.

You probably ask, "Did not he do enough? Can we stop now? "No. We must persevere, because the dust has done even more and we have come so close. For example, look at the map of the Milky Way. Where can all this dust come from?

It is here that the history of dust takes a more favorable turn. We have all heard that we are made of star dust. It would be futile to look for the source of our dust, but understanding the dust itself forces us to look to the stars.

The storms on Earth or on Mars that attract dust into the air are faint bursts against the colossal turbulence of stellar ruin. Stars can die in different ways depending on their size. Supernovae are the most spectacular. In a standard Type 1a supernova, a whole white dwarf star undergoes nuclear fusion, disintegrating completely and throwing material at more than 5,000 km / s. More massive stars undergo a collapse of the nucleus, expelling their outermost layers in the space of a deadly sneeze before what remains does not implode in a neutron star or a black hole.

In all cases, materials released into space form giant clouds that disperse slowly over millions of years. If they are in the presence of a black hole, they are then trapped in an accretion disk, accelerated, heated and excited by radiation and magnetic fields. The lucky ones can float to meet other stars, planets or other objects, or even run into other clouds of dust and gas. These interactions are very difficult to model – but there is no doubt that all these interactions are essentially dictated by the four fundamental forces of nature.

One of them is the force of gravity. When a gas / dust cloud becomes so large that its collective gravitational appeal prevents it from dispersing, it can collapse to form another star and live in another era.

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Together

In this way, the stars are cosmic engines. They keep matter – including dust – moving. They may not be the only ones to do so, but given the presence of stars throughout the (observable) universe, they certainly play a major role. When they do not return to life or come out of it, their gravitational force influences the trajectories of the other smaller bodies around them, including comets, asteroids, and other space rocks.

The solar system itself is considered to have been condensed into a large disk of dirt and dust made up of various elements surrounding a young Sun – a disk of remains of the birth of the star. Different planets have formed depending on the availability of different volumes of different materials at different times. It is believed that Jupiter came first and the inner planets, including the Earth, came last.

But whatever; life here had everything she needed to take root. Scientists are still figuring out what these ingredients might have been and where they came from. According to one theory, they included carbon and hydrogen compounds called polycyclic aromatic hydrocarbons, and they first formed – you guessed it – among the dust that snaked in the water. space.

They could then have been transported to Earth by meteors and comets, perhaps tilted to Earth's orbit by the gravity of the Sun. When a comet approaches a star, for example, the material on its surface begins to evaporate, forming a trail of gas and dust. When the Earth passes into an area where the remains of the tail and other small pieces of rock accumulate, they enter the atmosphere in the form of meteorite rain.

Dust is really everywhere and she rarely gets the credit she deserves. This has been and continues to be a painful part of everyday life. However, unlike our search for the extraterrestrial company, we are not the only ones to feel overwhelmed by the dust.