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Parker Probe; Touching the sun with the world’s fastest spacecraf

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Parker Probe
Studying the Sun up close and trying to uncover its secrets has been a long-held dream that has now become a reality thanks to the Parker Solar Probe.

Parker Probe; Touching the sun with the world’s fastest spacecraft

The sun has supported life on planet Earth for billions of years and has helped shape belief systems and legends throughout human history. This most luminous body in the sky is unavoidable and its existence is undeniable except in the rarest terrestrial environments. However, we still don’t really know how the sun works. Here we will talk about the Parker Probe.

The star of our system is much more complicated than it seems. Instead of the fixed and unchanging disk that our eyes see, the Sun is a dynamic and magnetically active star. The Sun’s atmosphere continuously ejects magnetized material that sweeps across the entire Solar System far beyond the orbit of Pluto, affecting all existing worlds along the way.

The long-standing dream of meeting the sun

Astronomers have studied the Sun for over a century. Using ground and space telescopes that are designed to withstand the impressive radiation of the sun’s burning face, they have stared at this star at every wavelength of the electromagnetic spectrum; But no matter how hard scientists have tried, they have not been able to reveal the secrets of the sun. Perhaps this failure is because until recently no telescope had come close enough to the Sun to really study it.

However, the situation changed recently. In the fall of 2021, for the first time in human history, a spacecraft flew into the Sun’s atmosphere and passed through the super-hot particles of the Sun’s corona. This achievement provided scientists with important information, with the help of which we can finally discover the secrets of the closest star to Earth. This daring spacecraft is called Parker Solar Probe.

Parker probe over the sun
Artist’s impression of the Parker probe’s entry into the Sun’s atmosphere.

The spacecraft was named Parker Solar Probe in honor of Eugene Parker, a famous American astrophysicist

For more than 60 years, scientists have dreamed of flying a spacecraft like the Parker Probe. In 1958, the year NASA was founded, the Space Studies Board of the National Academy of Sciences proposed that this newly established organization send a spacecraft into the orbit of the planet Mercury in order to study the environment around the Sun. Over the years, several research groups have presented different ideas for launching a solar probe; But none of the missions could get as close to the Sun as astronomers wanted. It took decades for the technology of heat shields and other elements to come together well and make the long-held dream of scientists a reality.

The original Solar Probe design in the 1990s intended to use Jupiter’s gravitational pull and enter a polar orbit that would send the spacecraft almost directly toward the Sun; But due to problems including the high cost and time of the mission, the plan was changed in the following years. In the early 2010s, the Sun exploration project was transformed into a less expensive project called Solar Probe Plus, and it was decided to use the gravitational assistance of Venus and a more direct flight path to reach the Sun. In May 2017, the spacecraft was renamed Parker Solar Probe in honor of Eugene Parker, a prominent American astrophysicist and the inventor of the term ” solar wind “. This was the first time that NASA put the name of a living person on one of its spacecraft. Finally, after decades of waiting for scientists, the Khurshid spacecraft was launched on August 12, 2018 (21 August 2018) and began its 7-year mission.

The mysterious star

The Sun’s atmosphere is made up of different layers just like the atmosphere of our planet. The Earth’s atmosphere has three layers, the troposphere, stratosphere, and mesosphere respectively, and the layers of the Sun’s atmosphere are the photosphere, chromosphere, and corona (sun’s crown). The surface of the Sun is often thought to be hotter than other parts, But the photosphere or the surface of the sun is actually not that hot. The temperature in this layer ranges from nearly 6200 degrees Celsius in the lower part to 3700 degrees Celsius in the upper part. This temperature is almost equal to the heat of electric arc welding. It is interesting to know that the air around a lightning strike can be up to five times hotter than the photosphere.

The strange thing is that the corona, as the outermost layer of the Sun’s atmosphere, is much hotter than the photosphere. The temperature of the corona, which starts approximately 2,100 km above the surface of the sun, reaches half a million to several million degrees Celsius, or at least 80 times the surface temperature. It’s like moving away from a fire, and the further you move away from it, the hotter you get. This unusual feature is what makes the achievement of the Parker Solar Probe even more impressive.

Parker Solar Probe
Parker solar probe in clean room. The heat shield of the spacecraft with its white ceramic coating can be seen at the top.

Why the Sun’s corona is much hotter than the Sun’s surface is one of the unsolved mysteries of the universe, and it is the task of the Parker Solar Probe to unravel it. As a result, the probe has the task of collecting information from the magnetic fields and charged particles of the solar corona and trying to answer this puzzle.

Overall, the scientific goals of the Parker probe are to determine the mechanisms that generate the fast and slow solar winds, the heating of the sun’s corona, and the transport of energetic particles. In order to achieve these goals, the probe must approach the Sun less than 10 solar radii from the center of the Sun (the radius of the Sun is 695,500 km) and spend at least 14 hours below 10 solar radii and at least 950 hours below 20 solar radii to make in situ measurements. spend Flying around the Sun, compared to other space missions whose destination is a planet, asteroid, or comet, presents unprecedented technical challenges to the spacecraft, which we will mention below.

Technical challenges of the Parker probe

Parker probe travels faster than any other spacecraft; So that in its last trip around the sun, it will fly over its surface at an incredible speed of 690,000 kilometers per hour. This speed is so high that the distance between Tehran and Kermanshah can be covered in less than three seconds. However, the first big problem facing Parker was actually getting to the sun. Although the sun’s gravity acts as an anchor for the entire solar system, it is not easy to approach.

To get a satellite out of orbit around the Earth, we need to reduce its angular momentum so that it falls towards the planet. This is what we have to do when trying to remove an object from orbit around the Sun; With the difference that in this case, we are at a distance of one astronomical unit or 150 million kilometers from the sun and we are moving at a speed of 30 kilometers per second.

Parker’s first big problem was getting to the sun

Any object that is launched from the earth will enter the path around the sun with the same orbital speed; This means that in order to achieve a shorter orbit around the sun, we must reduce the orbital speed of the spacecraft around the sun. Decelerating the spacecraft is an extremely energy-consuming operation; Especially when you add in the energy required to escape Earth’s gravity. So let’s assume that we first want to get our satellite from the surface of the earth to the orbit around the earth. This requires moving the satellite up to a speed of 9.2 km/s relative to the earth’s surface. Then, the satellite is placed in orbit around the Earth and moves around the Sun at a speed of 30 km/s.

After placing the satellite in the earth’s orbit, we have to perform an orbital maneuver called “Hohmann transfer”. By performing this maneuver, we change the spacecraft’s orbital energy to correct its perigee (closest distance to the Sun) or apogee (farthest distance from the Sun). To meet an outer planet like Mars, we need to increase the solar apogee by adding to the orbital energy of the spacecraft; While reaching an inner planet like Venus requires reducing the solar perigee by reducing the orbital energy. To reach Mars and Venus from Earth’s orbit, we need a delta way (change in velocity) of approximately 2.9 km/s and 2.5 km/s respectively. These values ​​are obtained using the following equation:

Delta V calculation formula

In the equation, the Greek letter mo, similar to the English u, is called the Sun’s planetary parameter, which is the product of the Sun’s mass. R 1 is the orbital radius of the mass from which we start moving. In this case, the distance of 150 million kilometers from the Earth to the sun is considered the orbital radius, and finally, R 2 is the perigee or zenith. If we calculate the DeltaV required for the Parker Solar Probe to reach its closest distance to the Sun (6.2 million km), we will arrive at a number of 21.4 km/s, which is more than 8.5 times the DeltaV needed to reach Venus.

The obtained Delta V number is considered extremely high and exceeds the capability of all rockets built so far. But four years ago, the Parker Solar Probe launched from Cape Canaveral, Florida atop the Delta 4 Heavy, the world’s second most powerful rocket after SpaceX’s Falcon Heavy. In order to give the probe additional thrust, Delta 4 was equipped with a special solid-fuel third stage, which provided an additional three kilometers per second delta velocity for the normally two-stage rocket.

However, even with this extra power, the probe could never get close to the Sun. In order to make his record-breaking flight, which was one-seventh of the record of Helios 2, NASA’s previous solar probe, Parker was assisted by the gravity of the planet Venus in an amazing way five times, and he is going to make two more flybys of this planet in 2023 and 2024.

The path of the Parker probe. The spacecraft shortens its orbit around the Sun with each Venus flyby.

Since Venus is a relatively low-mass planet, Parker needed this number of flybys. The amount of speed a planet can change is largely determined by its gravity, which in turn is determined by the planet’s mass. As mentioned earlier, Parker’s original plan was to get a gravitational boost from Jupiter that would bring the probe three times closer to the Sun; But this path was accompanied by some problems.

Since Jupiter’s orbit is very far from the Sun, the sunlight reaching the solar panels at the peak of Parker’s orbit was reduced by 25 times, and therefore the spacecraft needed much larger panels to provide its energy. This became problematic as the spacecraft orbited Jupiter and began accelerating toward the Sun. In this situation, the panels would be destroyed by the sun’s heat and could not be folded and hidden behind the solar shield.

Other options were available. The Parker builders could have used a radioisotope thermal generator; But this would dramatically increase the cost, weight, and complexity of the spacecraft. The real strength of Parker’s new and different flight path is getting more time and data to help scientists meet the rover’s mission goal of studying the Sun.

With the original plan to fly around Jupiter, the probe had only 100 hours of time in the target region around the Sun, and could only fly past the Sun twice before reaching the end of its eight-year mission. The new shorter path means that Parker Solar Probe will take less than 150 days to complete an orbit around the Sun, allowing scientists to collect more than 900 hours of data during the probe’s 24 orbits.

The main instruments of the spacecraft

Heat Shield

The change in the program was accompanied by a change in design, abandoning the original cone-shaped heat shield and using the flat, compact, and familiar shield used in other spacecraft. This shield is made of carbon foam with a thickness of 11.4 cm; A truly amazing material that is the product of one of the most capable material innovation labs called Ultramet. Under the scanning electron microscope, this carbon foam appears to be an extremely porous material with 97% of its internal volume being empty space, thus providing amazing insulation properties for the heat shield while benefiting from the thermal stability of carbon.

Parker’s heat shield is made of carbon-carbon composite and is exposed to temperatures of approximately 1400 degrees Celsius.

The next material is carbon-carbon composite, which is made by combining graphite with an organic binder such as bitumen or epoxy resin. This compound was applied to each side of the foam before being superheated and converting the glue into a pure form of carbon, creating a carbon-carbon composite. Finally, ceramic white was used to paint the sun-facing side of the shield to reflect the heat more.

But if the temperature of the Sun’s corona is at least half a million degrees Celsius, how can the probe enter it without melting? Although the Sun’s outermost layer is incredibly hot, it has a very low density. As a comparison, think of the difference between putting your hand in the oven and a pot of boiling water. (Don’t do this at home!) Hands can withstand much higher temperatures in the oven for longer than boiling water; Because they have to face many more particles in the pot of water.

Similarly, the Sun’s corona is less dense than the visible surface of the Sun; As a result, the spacecraft encounters less hot particles. In fact, while Parker is moving in an environment with a temperature of several million degrees Celsius, the heat shield facing the sun of the spacecraft only heats up to approximately 1400 degrees Celsius.

Read More: The Voyager Twins

Solar Probe Cup (SPC)

Other parts of the spacecraft, plus some specialized sensors and solar panels, had to be designed to fit under the shield’s shadow. But there are various tools that bravely step out from under the shadow of the heat shield; Like the cup of the solar probe, which is one of several sensors on board the spacecraft. This piece is undoubtedly Parker’s most impressive piece of technology, completely outside the scope of the sun shield’s protection; As a result, designers had to be very creative in using materials.

The Parker Solar Probe cup is a Faraday cup and part of the Solar Wind Survey Instrument (SWEAP); A device that can count and measure the properties of electrons and ions radiated from the sun and actually gives the spacecraft the ability to study the solar wind and objects ejected from the sun’s crown. This device basically works by applying an electric field to the grid placed in the mouth of the cup. By changing the voltage, it is possible to select or filter the particles that are able to enter the cup, and at the same time as the charged particles hit the collector plate at the bottom of the cup, more information can be obtained about the cause of the current. In practice, the cup is a very simple device; But facing temperatures of 1,400 degrees Celsius, which is just below the melting point of pure iron, the solar probe cup required some engineering innovations.

Solar Probe Cup (SPC)
Solar Probe Cup (SPC).

The first challenge was to choose a material for the electric grid that would create a selective electric field at the entrance of the cup. In addition to conductivity and resistance to heat, this network must also be machinable to make a spaced network on the scale of one hundred microns. For this purpose, the makers used tungsten; The same material used here on Earth in incandescent light bulbs. Thanks to tungsten, the lamps can survive the very high temperatures required to produce light. Tungsten filaments operate at a temperature of three thousand degrees Celsius; As a result, they are very durable against extreme temperatures. However, machining tungsten in a very fine mesh is difficult.

Micron-scale machining is not possible with traditional tools. By using these tools, as soon as the necessary force is applied to shave the metal, the mesh breaks. Instead, in such cases, lasers are usually used for engraving on materials; But since tungsten is very resistant to heat, the laser will not be able to melt it to form a network. Instead, the makers used acid printing.

Next, cables were needed that could supply the main power and carry the electrical signals away from the collector plate. Copper and aluminum, two common conductors on Earth, will be transformed into a pool of molten metal at the Parker Solar Probe position; As a result, they could not be used in any way. Each conductive cable in this part of the spacecraft must be made of niobium C-103, a special alloy consisting of 89 percent niobium, 10 percent hafnium, and 1 percent titanium. This strange aerospace material has also been used in the construction of all the components of the outer cover. Normally the wires are insulated with plastic outer coverings, But obviously, this option was not possible for the Parker space probe and the engineers had to use sapphire to ensure the insulation of the niobium wires.

To accomplish what is a relatively mundane task on Earth, Parker’s builders were forced to use strange materials. Other parts of the sensors beyond the solar shield are constructed in a similar manner. Magnetic field measuring instruments hidden behind the shield require antennas that extend beyond the solar shield to make measurements of the Sun’s magnetic field. These four antennas are also made of Niobium C-103.

Solar Panels

Solar panels were the next challenge. While orbiting the sun in its distant orbit, the spacecraft can fully open its solar panels without any problems; But as the probe begins its rapid return to the Sun, heat will become an increasing problem. By collecting solar panels, this problem can be partially dealt with; But the spacecraft must maintain some power to launch its scientific equipment during this important phase of the flight.

Parker has two smaller secondary panels that face the sun and are water cooled. This water is inside the solar panels and black radiators that are like titanium trusses right under the solar shield. It is pumped. This truss is very light despite its large size. The whole truss weighs only 22.7 kg, which considering the size of the structure, is very low weight even for titanium as a metal with low density. By performing detailed stress calculations, NASA engineers have ensured that the truss can use as little material as possible. This, of course, saves the launch weight; But the materials available to transfer heat from the heat shield to the bus (main body) of the spacecraft have also been minimized.

Edilo solar furnace
Edilo solar furnace in France.

It is difficult to test systems on the ground in the heat they are expected to encounter. The Edilo Solar Furnace is the most similar location to the environment that the Parker Probe systems will have to endure. Built on a mountainside in southern France, the facility uses ten thousand adjustable mirrors to focus light onto a concave mirror. Edilo solar furnace has the ability to reach a temperature of 3500 degrees Celsius; More than twice the temperature that Parker’s solar shield will experience.

Parts such as the Faraday cup and the solar shield were placed at the focal point of the concave mirror of the furnace and exposed to the temperatures that they must withstand when exposed to the sun. However, a piece like Faraday’s cup had to be tested while performing its sensory functions. To that end, the engineers needed a particle accelerator to simulate the electrons and ions from the solar wind that the cup would encounter. It was not possible to combine the particle accelerator with the solar furnace; As a result, researchers from the University of Michigan proposed the smart idea of ​​using four high-power IMAX projectors to simulate the sun’s heat. They also found that the Faraday cup actually performed better when heated; Because heat cleans the system from pollutants.

Much of the information obtained from the Faraday Cup is of little interest to the casual space enthusiast. They are the raw data that provide scientists with valuable clues about the nature of the Sun. However, one of the sensors on the spacecraft, which is in charge of transmitting images to the ground, can surprise us.

Wide Field Camera for Solar Probe (WISPR)

During a solar eclipse, we can observe a beautiful phenomenon: bright rings of light that appear around the sun. These extraordinary patterns are the result of bright electrons that move around the Sun on magnetic field lines and have been deformed by the pressure of the solar wind. We have been able to observe streams of energetic electrons from our Earth and solar observatories located at Lagrangian point 1, But we never managed to see them up close until recently.

After completing its final orbit and completing its mission, Parker will evaporate into the Sun’s atmosphere

As the Parker Solar Probe entered the corona on its ninth encounter with the Sun, it began capturing images of the surrounding space with its Wide Field Imager (WISPR), an array of optical telescopes. The images sent back to Earth are like a traveler’s view of a blizzard passing through on a dark night: glowing sub-particles streaming past as the probe plunges into the eye of the storm. These beautiful images will undoubtedly provide scientists with unique data about the nature of the sub-particles flowing in the Sun’s corona.

The path ahead of the Parker probe

The next close encounter of the Parker Solar Probe will take place on June 11, 1401, and the spacecraft will circle the Sun another 15 times for a total of 24 times in the next three years. With two more flybys of Venus in 2024 and 2025, Parker will break his records and get much closer to the Sun. On the last visit, the probe will reach a distance of 16.6 million kilometers from the Sun, which is almost seven times closer than any other spacecraft.

After completing the 24th orbit, the probe may have some fuel to continue orbiting the Sun; But Parker ultimately fails to ignite the thrusters necessary to keep his heat shield facing the Sun. The probe will then begin to rotate, and parts of the spacecraft not designed to see the sun will be exposed to full radiation.

The spacecraft will first break into large pieces and then become smaller and smaller. In the end, the entire probe, which is about the size of a small car, will be left with nothing more than tiny dust scattered across the Sun’s corona. However, Parker’s legacy will live on. The probe’s observations are expected to finally help solve questions that have been puzzling scientists for decades.

Space

Maybe the Earth is not doomed by the death of the sun

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A global discovery of an Earth-sized rock orbiting a white dwarf suggests a future where our planet could survive beyond the Sun.

Maybe the Earth is not doomed by the death of the sun

Will the sun one day destroy the earth? This may or may not happen. Astronomers have spotted a rocky planet the size of Earth orbiting a white dwarf, hinting at a future in which our planet outlives its star.

In 6 billion years, the sun will grow and become a red giant star. At this point, Mercury and perhaps Venus will be swallowed up, and for a long time, we thought that planet Earth would also be incinerated. But maybe the blue planet is not doomed, even though it may become an uninhabitable world in the next 6 billion years.

According to the New York Times, scientists have discovered a rocky planet orbiting a star that has passed its red giant phase. The planet now orbits a white dwarf, a smaller stellar body left over after a star burns out.

Importantly, the planet appears to have once been in the same position as the Earth now orbits our Sun. Before being swallowed up by its dying star, the rocky planet was pushed into a distant orbit, twice the distance between Earth and the Sun. In this way, the discovered world is considered the first rocky planet that has been seen rotating around a white dwarf.

A rocky Earth-like planet has survived the destruction of its star

“We don’t know if Earth can survive,” said astrophysicist Kaming Zhang of the University of California, San Diego, who led the study published in the journal Nature Astronomy. “If it survives, it will become such a system.”

The rocky planet is about 4,000 light-years away and in 2020, the South Korean Radio Astronomy Observatory discovered it using a process called gravitational microconvergence. The Korean team observed the star of the rocky planet while passing in front of a distant star, and that star magnified the amount of light reaching the telescope by a thousand times. This effect, known as convergence or gravitational lensing, makes it possible to identify very distant and faint objects.

That particular event was a one-off event, and the chances of further detailed observations are limited until powerful new telescopes can get a better look at the rocky planet in the future. But Dr. Zhang and his team were able to do more last year at the Keck Observatory in Hawaii and found out that the planet’s star is actually a white dwarf.

The researchers calculated that at least two objects are orbiting the white dwarf. One of them was a brown dwarf; That is, the failed star that had never ignited by nuclear fusion and was located at a great distance from the central star. But the other object is a planet with a mass of about 1.9 times that of Earth, which orbits closer to the star’s period and is therefore likely to be a rocky world.

By modeling the evolution of the star system, Zhang’s team calculated that the planet may have once been in a habitable orbit like Earth. The star was probably the same size as ours. “We expect the star to have been roughly the same mass as the Sun,” Dr. Zhang said.

A microlensing event revealing a white dwarfGravitational convergence shows the white dwarf shown by the vertical white lines. The researchers captured images of the star years before the event (a), shortly after the background star peaked in 2020 (b), and after it disappeared in 2023 (c).
Keck Observatory

But as the star ran out of fuel, it lost some of its mass, causing the rocky planet’s orbit to lengthen. The rocky planet escaped from the expanding red giant phase of the star and survived to the white dwarf stage.

A handful of gas planets have been found orbiting white dwarfs, but they were either in more distant orbits or had migrated inward and closer after the red giant phase. “If Dr. Zhang’s diagnosis is correct, this would be the first rocky planet orbiting such a star,” said Susan Mulally, an astronomer at the Space Telescope Science Institute in Maryland. “It’s definitely the smallest and clearest rocky planet we’ve ever found around a white dwarf.”

A handful of gas planets have been discovered orbiting white dwarfs

Stephen Kane, an astronomer at the University of California Riverside, noted that he was excited when he first read the paper. He has previously investigated whether planets can survive when their stars pass through the red giant phase, so he is intrigued by the new discovery. However, the presence of the brown dwarf complicates everything. If the brown dwarf was once closer to the star but moved outward, it could change the dynamics of the entire system, he explained. That means, maybe there are other planets that have been thrown out and the planets that are currently observed are among the survivors.

NASA is scheduled to launch the Nancy Grace Roman Space Telescope before 2027 and is expected to find more planets through gravitational microconvergence. Perhaps some of them are orbiting white dwarfs.

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Alien life may be hiding under the Martian ice cover

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Alien life may be hiding under the Martian ice cover. Martian dust ices in mid-latitudes are exposed to sunlight and provide a favorable environment for the search for possible Martian life.

Alien life may be hiding under the Martian ice cover

A new study suggests that the conditions necessary for photosynthesis on Mars may exist beneath the dusty ice cover in the Red Planet’s mid-latitudes.

Photosynthesis is a process by which living organisms such as plants, algae, and cyanobacteria can produce chemical energy. This process requires water and light to progress and produces much of the oxygen in the Earth’s atmosphere. According to the new findings, Martian ice layers of sufficient thickness can filter out intense solar radiation while still allowing sunlight to penetrate beneath them for photosynthesis, creating so-called “radiatively habitable” zones.

Since the process of photosynthesis is suitable for light, the new results should be considered in sufficient light conditions. While the findings don’t prove that life exists on Mars, or even existed in the distant past, they can give scientists ideas to search for. Aditya Kholler, a postdoctoral researcher and research supervisor at NASA’s Jet Propulsion Laboratory, says the Martian dusty ice in the mid-latitudes is exposed to sunlight and could be an accessible environment to search for life on Mars today.

NASA's Discovery OrbiterImages of the Red Planet from NASA’s Mars Exploration Orbiter (MRO).

Earth vs. Mars

Both Earth and Mars are located in a range known as the Sun’s life belt; A region around a star where the temperature is favorable for the flow of surface liquid water. Although 71% of Earth’s surface is covered by liquid water oceans, Mars has a mostly dry landscape.

Discoveries of Mars rovers such as Curiosity and Perseverance have shown that conditions on Mars are different. Surface features such as dry lake beds and river forks discovered by these robots indicate the presence of surface liquid water billions of years ago. Additionally, Mars missions such as the Mars Reconnaissance Orbiter (MRO) have often discovered water ice in unexpected areas.

According to scientists, Mars lost its liquid water billions of years ago; Just as the planet’s magnetic field weakened (Earth’s magnetism is still very strong) and much of its atmosphere was lost. Thus, there were few barriers to surface water evaporation. The absence of a thick atmosphere also means that today’s Mars is under the bombardment of harmful ultraviolet radiation from the sun, which is fatal for living organisms and can destroy the complex molecules needed for life.

Waterholes in Terra Sirnum areaNASA’s Discovery Orbiter image of craters in the Cyrene region of Mars.

Unlike Earth, Mars does not have an ozone protective shield; As a result, the level of surface ultraviolet radiation is 30% higher than that of the earth; Therefore, photosynthesis on Mars probably occurs in places that are inside the dusty ice; Because the dusty ice cover can block harmful UV rays on the surface of Mars, and liquid water is highly unstable due to the planet’s dry atmosphere.

Using computer simulations, the researchers found that Martian dusty ice may melt from the inside and that the overlying ice cover prevents shallow subsurface liquid water from evaporating in the dry Martian air. According to Kholer:

Thus, two key elements for photosynthesis could be present in mid-latitude Martian dust ices. Photosynthesis requires sufficient amounts of sunlight as well as liquid water. Two previous independent simulations of dense Martian snow show that if small amounts of dust (less than one percent) are present in the snow, subsurface melting could occur in the mid-latitudes of present-day Mars.

“With the discovery of dusty ice that was exposed a few years ago within snow masses in Martian glaciers, there is a mechanism for subsurface melting that could underlie the formation of shallow subsurface liquid water,” Kholer added. According to Kholer, the dusty ice on the ice cap can block UV radiation from the surface of Mars and also allow sunlight to penetrate below the surface for photosynthesis.

Watershed of Dao Wallis areaAn image from NASA’s Discovery Orbiter of a puddle in the Dao Wallis region of Mars.

The depth required for the formation of radiative habitable zones depends on the amount of dust in the ice. Very dusty ice can block a lot of sunlight, the researchers’ simulations show. However, ice with 0.01 to 0.1 percent dust allows for the formation of a radiative zone between 5 and 38 cm deep. Less contaminated ice allows for a deeper and wider radiation zone at a depth between 2.2 and 3.1 meters.

According to researchers, the polar regions that have the most ice on Mars are too cold for habitable radiation zones; Because they do not have the subsurface melting mechanism. Such a mechanism probably occurs in the middle latitudes of the Red Planet.

Scientists have taken scientific support for their theory from evidence on planet Earth. Kholer says:

I was surprised to learn that similar areas for life exist within dusty and sedimentary polar ice. These areas are called cryoconite cavities and are formed when dust and sediment on the ice melts into it because it is darker than the ice.

Dust ice cavities in the earth's glaciersEvidence from Earth: Cryoconite-formed cavities on the Matanuska Glacier, Alaska, 2012

Every summer, due to heating by sunlight, liquid water gathers around the dark dust inside the ice. This happens because the ice is semi-transparent, allowing sunlight to penetrate below its surface. According to Khüler, the researchers discovered that the tiny organisms that live in these shallow subsurface habitats on Earth usually go dormant in the winter, when there isn’t enough light to form liquid water in the dusty ice.

Of course, none of the above findings mean that photosynthetic life exists on Mars or probably ever existed; But it could inspire further research into the possibility of radiation habitats on the Red Planet. Kholer adds:

I am working with a group of scientists on improved simulations of where and when the ice melts on present-day Mars. Additionally, we are recreating these dusty ice scenarios in the lab to investigate them in more detail.

The results of the research were published on October 17 in the journal Communications Earth & Environment.

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Why is it still difficult to land on the moon?

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More than half a century after the first spacecraft to reach the moon, a successful landing on Earth’s only moon remains a challenge for space agencies and private companies.

Why is it still difficult to land on the moon?

This year, the private company Spacel and the Indian Space Organization both met tragic ends when they tried to land their spacecraft on the surface of the moon. Despite the astonishing leaps made in recent decades in computing, artificial intelligence and other technologies, it seems that landing on the moon should be easier now; But recent setbacks show that we still have a long way to go with safe and trouble-free landings on the surface of Earth’s only moon.

50 years after sending the first man to the surface of the moon, the question arises as to why safely landing a spacecraft on Earth’s nearest cosmic neighbor is still a difficult task for space agencies and private space companies. Stay with Zoomit to check the answer to this question.

Why is the lunar landing associated with 15 minutes of fear?

Despite the complexities of any space mission, sending an object from Earth into orbit around the moon today is easy. Christopher Riley, the director of the documentary film In the Shadow of the Moon produced in 2007 and the author of the book Where We Stood (2019), both of which are about the history of the Apollo 11 mission, explained the reasons for the difficulty of landing on the moon in an interview with Digital Trends. is According to him: “Today, the paths between the Earth and the Moon are well known, and it is easy to predict them and fly inside them.”

Chandrayaan-2
Chandrayaan 2 mission launch

However, the real challenge is getting the spacecraft out of orbit and landing it on the lunar surface; Because there is a delay in the communication between the Earth and the Moon, and the people in the control room who are present on the Earth cannot manually control the spacecraft in order to land it safely on the Moon. As a result, the spacecraft must descend automatically, and to do so, it will fire its descent engines to slow its speed from thousands of kilometers per hour to about one meter per second, in order to make a safe landing on the lunar surface.

For this reason, the director of the Indian Space Research Organization (ISRO), who was trying to land the Vikram lander last month, described the final descent of the spacecraft as “frightening 15 minutes”; Because as soon as the spacecraft enters the landing stage, the control of its status is out of the hands of the mission control members. They can only watch the spacecraft land and hope that everything goes according to plan, that hundreds of commands are executed correctly, and that the automatic landing systems gently bring the spacecraft closer to the surface of the moon.

The Great Unknown: The Landing Surface

One of the biggest challenges in the final descent phase is identifying the type of landing site. Despite the availability of instruments such as the Lunar Reconnaissance Orbiter (LRO) that can capture amazing views of the lunar surface, it is still difficult to know what kind of surface the spacecraft will encounter when it lands on the moon.

Beresheet crash site
Left: Breshit crash site. Right: The ratio of the before and after images highlights the occurrence of minor changes in surface brightness.

Leonard David, author of Moon Fever: The New Space Race (2019) and veteran space reporter, says:

The Lunar Reconnaissance Orbiter is a very valuable asset that has performed really well over the years; But when you get a few meters above the surface of the moon, complications appear that cannot be seen even with the very powerful LRO camera.

Even today, despite the imaging data available, “some landing sites still have unknown remains,” Riley says. He notes that the Apollo 11 mission included an advantage that today’s unmanned landers lack, which is the presence of an astronaut’s observer’s eyes that can closely observe the surface of the spacecraft’s landing site. As you probably know, in the mission that led to the landing of the first man on the surface of the moon, the Eagle computer was guiding the spacecraft to a place full of boulders; But to avoid hitting the rocky surface of the moon, Armstrong took control of the spacecraft himself and landed it on a flat surface.

Apollo 11 / Apollo 11

The uneven surface of the landing site had caused many problems in previous lunar missions such as Apollo 15. In this mission, the astronauts were told that as soon as the spacecraft touched the surface of the moon, they should turn off the engines to prevent dust from being sucked in and the risk of a return explosion. But the Apollo 15 spacecraft landed in a crater, and because of this, one of its legs came into contact with the surface earlier than the others. When the crew shut down the engines, the spacecraft, moving at a speed of 1.2 meters per second, experienced a hard landing. The lander landed at an oblique angle, and although it eventually landed safely, it nearly overturned, causing a fatal disaster.

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The difficult landing of Apollo 15 introduced another complicating factor in lunar landings: lunar dust. The Earth’s moon is covered with dust that is thrown into the air by any movement and sticks to everything it comes in contact with. As the spacecraft approaches the surface of the moon, huge plumes of dust are kicked up that limit the field of view and endanger the spacecraft’s electronics and other systems. We still do not have a solution to deal with the dust problem.

An achievement that has been achieved before

Another reason why the moon landing remains a challenge is that gaining public support for lunar projects seems difficult. Referring to Neil Armstrong and Buzz Aldrin, the two astronauts who walked on the moon during the Apollo 11 mission, David says, “We convinced ourselves that we had sent Neil and Buzz [to the surface of the moon]; “As a result, when it comes to lunar missions, people may say we’ve been there before and we’ve had this success.”

Apollo 11 / Apollo 11

But in reality, our understanding of the moon is still very little, especially in relation to long-term missions. Now, with a 50-year gap between the Apollo missions and NASA’s upcoming Artemis project, the knowledge gained has been lost as engineers and specialists retire. David says:

We need to recover our ability to travel into deep space. We haven’t gone beyond near-Earth orbit since Apollo 17 and since 1972. NASA is no longer the same organization that put men on the moon, and there is a whole new generation of mission operators.

The importance of redundancy

As the first private spacecraft entered into orbit around the moon, the Space project was of considerable importance; But its failure to land smoothly on the surface of the moon made the achievement of landing on the surface of the moon still remain in the hands of governments. However, we can expect more private companies, such as Jeff Bezos ‘ Blue Origin, which is developing its lunar lander, to target the moon in the future. According to Elon Musk, even the giant SpaceX Starship spacecraft, which is being built with the ultimate goal of sending a human mission to Mars , can also land on the moon.

According to David, private companies’ participation in lunar landings has advantages such as increased innovation. However, companies are under pressure to save money, and this can lead to a lack of redundancy and support systems that are essential in the event of errors and malfunctions. Lunar rovers typically include two or even three layers of support systems. David is concerned that private companies will be encouraged to eliminate these redundancies in order to cut costs and save money.

Crew Dragon
Crew Dragon SpaceX passenger capsule

“We saw Elon Musk’s Dragon capsule catch fire after a failed test on the stand,” says David, referring to the explosion of the SpaceX spacecraft in April, which had no crew on board. “This accident was kind of a wake-up call about how unpredictable the performance of spacecraft can be.” David compared the Crew Dragon incident to the Apollo 1 disaster, which killed three NASA astronauts during a test launch in 1967.

Another problem related to the lack of redundancy systems is the lack of information needed when an error occurs. As for the recent landings, it seems that the SpaceX crash was caused by human error; however, it is not clear what caused the failure of Chandrayaan 2 in the calm landing, and it is possible that without the necessary systems to record and send information to the lander, we will never find out the main reason for the failure of this mission. Without the required data, it becomes much more difficult to prevent problems from reoccurring in the future.

The future of lunar landings

Currently, many projects are underway to facilitate future moon landings. Ultimately, we need to be able to build the necessary infrastructure for a long-term stay on the moon.

Moonrise Project
Conceptual design of Moonrise technology on the moon. On the left side is the Alina lunar module, and on the right side, the lunar rover equipped with Moonrise technology melts the lunar soil with the help of a laser.

If we can make long-term stays on the moon possible, or even build a permanent base there, landing spacecraft on the lunar surface will be much easier. By constructing the landing sites, a flat, safe, and free surface of unknown debris can be created for the landing of surface occupants. For example, researchers are currently conducting research at NASA’s Kennedy Space Center to investigate the feasibility of using microwaves to melt the lunar soil (regolith) and turn it into a hard foundation so that it can be used as a landing and launch site. The European Space Agency is also investigating how to use 3D printing to create landing sites and other infrastructure on the moon.

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Other ideas include the use of lidar remote sensing systems, which are similar to radar systems; But instead of radio waves, it uses lasers to land the spacecraft. Lidar technology provides more accurate readings and uses a network of GPS satellites to help guide the spacecraft during landing.

The problem of public support

As important as technology is, public interest and support are essential to the success of the lunar landing program. “Apollo had enormous resources that are perhaps only comparable today to China’s space program,” says Riley. “Remember that Apollo carried the best computer imaginable, the human brain.” It goes without saying that there is an element of luck involved in every landing.

Mike Pence
US Vice President Mike Pence speaking at the 50th anniversary of the Apollo 11 mission

Finally, there is the question of what kind of failure is acceptable for people. David says:

I think we have to be serious about the fact that we’re probably going to lose people. There is a serious possibility that the manned lunar lander will crash and kill the astronauts inside. The American people continued to support NASA despite the failures and bad luck of the Apollo program, But at that time there was a lot of pressure to compete with the Soviet Union. Without the bipolar atmosphere of the Cold War and the space race, would people still support missions with human lives in between?

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