Everything you need to know about the Universe and Water

At the dawn of space exploration, it was hard for ordinary people to believe that there was water outside our planet, something that caused uneasiness and fantasy expectations linked to our feelings of loneliness in the cosmos.

Two centuries ago, in 1887, the Italian astronomer Giovanni Schiaparelli observed the planet Mars with a 28-centimeter diameter telescope and drew a map of the planet, including some straight lines that he thought he saw, calling them "channels" as an artificial way of naming them similar to the "seas" with which certain sites observed on the Moon had been named, knowing full well that they were not bodies of water.

However, years later, in 1895, Percival Lowell, an American millionaire, and patron of astronomy became obsessed with the Schiaparelli canals and convinced himself that such straight lines were true aqueducts that carried water to some imaginary civilization, without any evidence, thus starting the world fever for the non-existent Martians and their chimerical aqueducts.

It was not until the twentieth century, in 1957, that humans were able to explore our neighborhood technologically with the launch of the Soviet satellite Sputnik. Two years later, in 1959, the unmanned Soviet ships Lunik 1 and 2 landed on the moon. However, our concern about the existence of water outside the planet could not be confirmed or denied outright by evidence, not even by the human presence of the United States on our natural satellite in the 1960s and early 1970s in the Apollo expeditions.

In the 1990s, the U.S. robotic satellites Clementine and the Moon Explorer suggested the presence of frozen water at the poles of the Moon. Finally, with facts, with evidence, by 2012, the U.S. Space Agency's Lunar Reconnaissance Orbiter obtained data that allowed it to claim that a quarter of the material in Shackleton Crater is frozen water.

Thanks to the advancement of scientific knowledge, better and more consistent theoretical tools and materials, technological developments and innovations, space exploration today have reached little beyond the Solar System; man-made artifacts have reached the farthest planets and explored their natural satellites.

We know that some of Jupiter's satellites have water. Callisto is made up of 40% ice and 60% rock and iron. Europa has liquid water under its icy surface; Ganymede has a rocky core wrapped in a large mantle of water and ice. Orbiting the planet of the rings, Saturn, Enceladus has water volcanoes, Titan is composed of frozen water and rocky material.

In January 2013, the European Space Agency's (ESA) Mars Express probe, while exploring a region called Tagus Valles, observed craters that once held water and there are still signs of it. In one of them, in its upper-right corner, a small, winding river channel could be seen, further evidence of the existence of water at some point in its past. More recently, in March, NASA's Mars Curiosity Explorer found evidence of water layers in rock minerals.

Since its inception, there has been water in the Universe

The Universe originated 13.7 billion years ago. Except for primordial hydrogen and helium, all the elements have been produced by thermonuclear activity in the stars, and in their collapses.

The first water molecules, composed of two hydrogen atoms linked to one oxygen atom, date back 12 billion years, just 1.7 billion years after the universe originated, according to reports by astronomers at the California Institute of Technology through its Submillimeter Observatory and by European Space Agency astronomers through the telescopic array called ALMA (Atacama Large Millimeter Array).

In the first case, it is a huge cloud of water vapor surrounding a powerful black hole. In the second case, astronomers detected nascent galaxies containing water molecules. Water, then, has been abundant in the Universe since its inception.

In the Universe near our Solar System, only two thousand light-years away, in 2001, Mexican astronomers Luis Felipe Rodriguez, Salvador Curiel, Jorge Cantó and the Spaniard José María Torrellas discovered a newly formed star wrapped in a surprising water vapor bubble, in the constellation of Cepheus.

Our "blue planet" actually has very little water

On our planet, the water footprint is surprisingly subtle. What looks like huge oceans, rushing rivers, cloud formations, the eternal ice, all come down to a thin surface layer that covers only three-quarters of the Earth's great rocky and mineral mass, equivalent to just the film of moisture left over when we pull out an orange after dipping it in a bucket of water.

If all the water on Earth could fit into a one-liter bottle, 975 milliliters would be saltwater, 25 would be ice or inaccessible groundwater, and just a third of a milliliter - the equivalent of a drop - would be fresh liquid water, which we need to live. And to live, we need to share this small drop of water with plants and animals, with ecosystems.

Mexico has just 0.1 percent of the planet's available freshwater. It rains approximately 1,500 cubic kilometers of water each year across the country, equivalent to a pool the size of the Federal District one kilometer deep. In addition, nearly three-quarters of that rainwater evaporates. The country is semi-arid, so it is important to consider water not only as a vital element, but also as a strategic factor for development.

If there is a lack of water, we die; if there is too much, we die too. Floods and droughts are equally lethal for our species. Despite advances in technology and adaptation to the environment, we are not prepared to face natural phenomena. The human activities that affect the excess or lack of water are deforestation, intensive agriculture and livestock, unplanned and poorly managed urbanization, poor waste management and consumerism.

We talk about the water crisis when in reality there is a crisis of knowledge about water and its use. Our way of relating to water, until today, has been devastating. We pollute it faster than nature can clean it up and we do not realize that we are part of its cycle, the hydrological cycle.

Adequate water management is fundamental to achieving social well-being, economic development and the preservation of ecological wealth. To the extent that citizens take part in water management in an informed manner, the decisions made will imply a stronger commitment and projects can transcend government cycles.

Water on Earth

The most current theories about the origin of water on Earth consider that part of the water was already in the material from which the planet was formed and that it emerged to the surface, thanks to volcanic activity. Another small part of the water could have been brought in by bodies like comets and asteroids.

Geologists and geophysicists believe that, in the first millions of years of the Earth's existence, when volcanic activity was more intense than now, there were periods when the rains were torrential.

Since then the continents began to move to their present configuration, in fact, they still move, but at a speed that is almost imperceptible to humans. For example, it is known that the peninsula of Baja California moves at a speed of 3 millimeters every year, scientists believe that a moment will come when it will fall away from the continent but none of us who live now will be able to witness it.

The slow movement of the continents created ups and downs in the terrain and gave rise to the great oceans and the primary seas. Just as it happens now, back then, the water evaporated and formed clouds, these moved towards the continents and there they discharged their water, the water drained eroding the land and forming rivers, many of which now no longer exist.

Part of the erodable material through which the water drained was also porous and that is where the vital liquid began to filter, forming the great aquifer systems. The water found there is considered young because, although it is tens of years old, compared to the age of the Earth it is much more recent.

Water on Earth. Image credit: Pixabay
Water on Earth. Image credit: Pixabay

The water of the oceans, from its origin, was rich in chlorides, when it evaporated it was leaving a great part of its salts in the ocean and it was transported thanks to the clouds to the continents where it descended in rain form, but with fewer salts. Thus the water of our planet was separated into freshwater and saltwater.

The ice concentrated in the North and South Poles has formed thanks to the fact that solar energy does not reach the Earth in a uniform way, the equator is warmer and the poles are colder, that is why in these places the water freezes and accumulates.

Although Mexico is a very fortunate country from the point of view of biodiversity and other energy resources, from the point of view of water it is unfortunate.

The movement of the plates, when the continents were formed, constituted what is known as the Altiplano. An altiplano is a kind of elevated plateau that is generally found between mountains, in the case of Mexico, the Sierra Madre Occidental, and the Sierra Madre Oriental. These orographic conditions hinder the existence of large rivers, such as the Mississippi or the Amazon.

The mountains also restrict the arrival of the rain to the center of the country, both from the Atlantic and the Pacific Oceans, and have contributed to the loss of the lake systems previously present. In addition, the distribution of water in Mexico is very unfortunate, with large volumes in the south where there are few population centers, and very little water in the north where there are larger cities.

Mexicans must know the origin of water, and what it costs to pipe and distribute it, in order to be aware that its origin is not divine, nor is it a free resource, so that the authorities can make informed decisions and demand better management of this resource.

Water as a tool for astronomical research

On the slopes of the Sierra Negra and Pico de Orizaba volcanoes, on the borders of the states of Puebla and Veracruz, is located the Gamma Ray Observatory HAWC (High Altitude Water Cherenkov Observatory).

At an altitude above sea level of 4,100 m, this unique observatory is capable of mapping the sky in cosmic rays and high energy radiation. Unlike the classical concept of mirrors, lenses or antennas, the HAWC gamma-ray observatory is an array of 300 water containers, each 4.5 m high by 7.3 m in diameter, at the bottom of which ultra-sensitive light detectors have been placed to study the most energetic violent phenomena in the Universe.

HAWC's astrophysics

Gamma rays (very high-frequency electromagnetic radiation) and cosmic rays (subatomic particles generated by astrophysical processes) can be the product of the most energetic events in the Universe, such as the explosion of a supernova, the collision of two neutron stars or the evolution of supermassive black holes.

How HAWC works

When these particles head for our planet, they continuously bombard the upper layers of the atmosphere and interact second by second with the atoms in their path, triggering a cascade of particles that gradually lose energy.

When this cosmic cascade enters HAWC's water tanks, the particles that form it, which travel faster than light inside the water, create an effect similar to that of a supersonic plane producing a shock wave in its wake, only in this case they produce a trail of visible, blue light instead of a rumble. This radiation, called Cherenkov light (which lets us know that the particles have passed through) is measured by electronic detectors at the bottom of the tank, revealing their existence.

By reconstructing the signal observed by all the tanks together using electronics and high-precision computer equipment, it is possible to determine the energy, direction, arrival time and nature of the particle responsible for the cascade.

This is how HAWC works
This is how HAWC works

Enemies of water

How HAWC containers are made

The tanks have a polyethylene cover, like those used in artificial lakes, which is enriched with carbon, so that it is more opaque to outside light. The darkness inside the tanks is very important, as the Cherenkov light produced by the particles is very dim, and the darker the medium, the easier it will be to detect. This feature also prevents the growth of bacteria.

At the same time, HAWC requires very transparent water, so the water stored in the tanks must have a minimum attenuation of 15 meters (it is as if in a pool you could clearly see a person underwater at a distance of 15 meters).

The water in the HAWC tanks comes from natural wells and from the melting of the Pico de Orizaba. After being piped in, with the support of an existing pipe network, the water is taken to the purification plant on site. There, the water is treated with carbon filters and ultraviolet light to kill all kinds of organisms that the mountain water might bring with it, such as bacteria and algae. In addition, it is very important to eliminate chlorine, as it is the greatest enemy of water transparency.

Why water?

Water is cheap and non-toxic. It takes more than 200,000 liters to fill each of the tanks. In addition, the refractive index of water gives us a 45-degree angle to observe Cherenkov radiation, making it easier to observe and detect.

HAWC is an international project in which the Institutes of Astronomy, Physics, Nuclear Sciences, and Geophysics, all at UNAM, as well as the National Institute of Astrophysics, Optics, and Electronics (INAOE), the National Council of Science and Technology (CONACyT), and U.S. institutions such as the National Science Foundation (NSF), Los Alamos National Laboratory, and the University of Maryland participate.

Kamiokande

The Kamiokande family of underground experiments uses ultra-pure water to detect the most furtive particles in the Universe.

In the Sun's core, at temperatures of 15 million degrees, hydrogen atoms are converted into helium. Positrons are also created: particles with a positive electrical charge; some of the energy that gives the Sun its glow also originates, and it has to travel hundreds of thousands of years from the core to reach the upper atmosphere, which we see with the naked eye, and from there make its way through outer space to the planets; simultaneously trillions of trillions of particles per second, known as neutrinos, are created.

The equations arising from the theories predicting the number of neutrinos generated on the Sun were put to the test in the 1960s. With concern, it was discovered that only a third of the expected neutrinos were detected. Giant detectors with ultra-pure water would help solve the puzzle.

Neutrinos are atomic particles with no electrical charge. They interact virtually unaffected by the rest of the particles in the universe. The lack of interaction between neutrinos and other particles makes them very difficult to detect.

Just over 100 kilometers from Tokyo, Japan, on the mountainous outskirts of the small town of Kamioka, a deep abandoned mine has been put to new use; the results of their new profession are changing the way we understand the Universe. A thousand meters below the surface, inside a huge cylinder 41 meters high by 39 meters in diameter, the size of almost half a football field; with 50 thousand tons of ultra-pure water, a detector is working that is discovering the most furtive particles coming from space.

The depth of the mine helps only those particles that do not interact with the rest of the atoms in the atmosphere and on the earth's surface. To solve the riddle of the 66% missing neutrinos predicted by the theory, KamiokaNDE (Kamioka Nucleon Decay Experiment) was designed and built in the 1980s, a giant pit with 3,000 tons of ultra-pure water, replaced a few years later by Super Kamiokande, which stores 50,000 tons of water.

The ultra-pure water must meet several requirements: it must regulate the proliferation of bacteria, particles, organic, metallic and anionic contaminants (electrically charged particles). Around the water, there are thousands of photomultipliers: instruments designed to detect very weak flashes of light and multiply their brightness millions of times in order to study it.

Light travels in a vacuum at 300,000 kilometers per second. The neutrinos created in the solar core travel at that same speed. In water, which is denser than a vacuum, light travels at 225,000 kilometers per second. Therefore, when a neutrino enters the water, it interacts with an electron or nucleus of water atom and generates a particle that emits light. This light phenomenon is known as Cherenkov radiation. About 7 billion neutrinos generated by the Sun every second pass through the Earth, per square centimeter. Since neutrinos rarely interact with other particles, it takes thousands of tons of ultra-pure water composed of billions of quadrillions of atoms and electrons to generate a few flashes whose brightness will be multiplied and recorded.

This is how the Kamiokande family experiments helped to solve the riddle of the elusive solar neutrinos. First, the equations derived from the theory were proven correct. In addition, the neutrinos were assigned a mass value, previously considered to be zero. It was discovered that there are three types of neutrinos (tau, muon, and electron) and that they can change the type from the electron neutrino generated in the core of the Sun to the other two types, thus solving the problem of the solar neutrino deficit.

Additionally, neutrinos produced by a distant stellar explosion, supernova 1987a, thousands of light-years away, were detected. Finally, an enigma that existed, similar to solar neutrinos, was solved with the neutrinos of the Earth's atmosphere. Masatoshi Koshiba's experiment won him the 2002 Nobel Prize in Physics. Thus, water plays an important role as a research tool to discover one of the most furtive particles in the Universe.


Source: La Noche de las Estrellas, with information from Dr. Ramiro Rodríguez Castillo, a researcher at the UNAM Geophysics Institute, interview with Dr. Magdalena González, co-coordinator of the scientific exploitation of the HAWC observatory, and Communication Committee of the La Noche de las Estrellas