My Science School

Launched on May 28, 1971, Mars 3 was one among a pair of identical spacecraft. While its lander stopped transmitting data after less than 20 seconds, it nevertheless represents the first successful soft landing on Mars. A.S.Ganesh hands you the details about the Mars 3 mission...

When we talk about the space race between the Cold War adversaries the US. and the Soviet Union, we usually discuss the race to land the first human beings on the moon. Soon after this was achieved, however, attention shifted to our neighbouring planet Mars. The first successful soft landing on Mars was achieved by the Soviet Union with their Mars 3 mission.

At this initial period of planetary exploration, both these space superpowers tended to launch pairs of spacecraft as a precautionary measure. The idea was to have one as the backup. of another, so that at least one of them succeeded in its efforts even if the other failed completely in its objective.

It therefore comes as no surprise that the Mars 2 and Mars 3 missions consisted of identical spacecraft. With a bus/orbiter module and an attached descent/lander module, the combined mass of the spacecraft, with fuel, was approximately 4,650 kg. The Mars 3 spacecraft was 4.1 metres high. 5.9 metres across the two solar panel wings and had a base diameter of 2 metres.

Primary objectives

The primary objective of the Mars 3 orbiter was to image the martian surface and clouds. determine the temperature on Mars, and measure properties of the martian atmosphere. among others. These were in addition to serving as a communications relay to send signals from the lander to Earth.

Mars 3 was launched on May 28, 1971, just nine days after Mars 2 had been successfully launched. Ten days later, on June 8, a mid-course correction was made after which Mars 3 was involved in a three-way race with Mars 2 and U.S.' Mariner 9 to become the first spacecraft to orbit Mars.

Even though Mariner 9 was last off the blocks, having been launched on May 30, it became the first to reach Mars on November 14. Mars 2 reached Mars on November 27 and Mars 3 made it to its destination on December 2.

Achieves soft landing

 Less than five hours before reaching Mars, the descent module of Mars 3 had been released. Having entered the martian atmosphere at roughly 5.7 km/s, a combination of aerodynamic braking, parachutes, and retro-rockets allowed the lander to achieve a soft landing. With the Mars 2 lander having crashed, this made the Mars 3 mission the first ever to achieve a soft landing on Mars.

Only just though, as the lander stopped transmitting and the instruments stopped working less than 20 seconds after the successful landing. While the reasons remain unknown, the massive surface dust storms that were raging at the time of landing could have caused the lander to stop working.

As the orbiter had suffered a partial loss of fuel, it couldn't put itself into the planned 25 hour orbit. Instead, a truncated burn was performed by the engine in order to put the spacecraft into a 12 day, 19 hour long orbit about Mars.

20 orbits around Mars

A large volume of data was sent hack by Mars 2 and Mars 3 orbiters from December 1971 to March 1972, even though transmission continued till August. On August 22, 1972, an announcement was made stating that Mars 2 and Mars 3 had completed their missions. While Mars 2 had completed 362 orbits of the red planet, Mars 3 had performed 20 orbits.

Apart from the 60 images received from the probes, the data provided by them revealed mountains as high as 22 km, atomic hydrogen and oxygen in the upper atmosphere, and surface temperatures and pressures. The data gathered not only provided information on the martian gravity and magnetic fields, but also helped create surface relief maps.

Mars 3 was back in the news four decades later in April 2013 when citizen enthusiasts found features of its hardware in a five-year-old image from NASA's Mars Reconnaissance Orbiter. The debris in the images resembled what might have been the parachute, heat shield, terminal retrorocket and lander. Regardless of whether these were the debris of the Mars 3 lander or not, the mission did successfully become the first ever to achieve a soft landing on our neighbouring red planet.

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The satellite has been designed to conduct a landmark survey of the world's oceans, lakes, and rivers from space for the first time.

NASA, the U.S. space agency, recently launched a satellite called SWOT. What is its objective and how will it help us? Let's find out.

Its mission

SWOT, short for the Surface Water and Ocean Topography satellite, was recently launched from California to make a comprehensive survey of the world's oceans, rivers, and lakes from space for the very first time. Dubbed a "revolution in hydrology", SWOT, an SUV-sized satellite flying at a height of 890 km, will offer an unprecedented, clear view of the water bodies, while tracking the rise in sea levels, as well as rivers, lakes, and reservoirs. The satellite is expected to offer key insights into how these bodies of water influence climate change and factors such as how much more heat and carbon dioxide oceans can absorb. Oceans are estimated to have absorbed more than 90% of the excess heat trapped in Earth's atmosphere caused by human-induced greenhouse gas emissions. With climate change accelerating, some regions are experiencing extreme droughts. while others extreme floods, along with changing precipitation patterns. According to researchers, the observations of SWOT will improve our understanding of how water moves around Earth, its circular currents in oceans, etc. This will help predict floods in areas where there is too much water, and manage water in places that are prone to drought.

How will it work?

The global water survey satellite will measure the height of water in freshwater bodies and the ocean on more than 90% of Earth's surface - which it will track at least once every 21 days. Researchers will be able to get data on millions of lakes, rather than the few thousands currently visible from space. The technology employed by SWOT is called KaRin, a Ka-band radar interferometer. The radar sends down a signal which is reflected back by the water surface. This echo is received by two antennas, resulting in two sets of data providing high accuracy for water detection and resolution. The data, compiled from the radar sweeps of the planet, will be used to bolster weather and climate forecasts and aid in managing scarce freshwater supplies in drought-stricken areas.

Who developed it?

The satellite is a billion-dollar project developed jointly by NASA and France's space agency CNES, with contributions from the Canadian space agency and the U.K. space agency. It was carried onboard a spacex Falcon-9 rocket from the Vandenberg U.S. Space Force Base. SWOT will start collecting scientific data in about six months time after undergoing checks and calibrations. The satellite's components were built primarily by NASA's Jet Propulsion Laboratory near Los Angeles and CNES.

According to SWOT'S project head at CNES, Thierry Lafon, the mission is meant to last for three-and-a-half years, but could be extended. The U.S. and French space agencies have worked together in the field for over three decades. An earlier satellite developed by the two agencies, TOPEX/Poseidon, improved understanding of ocean circulation and its effect on global climate. It also aided the forecast of the 1997-1998 El Nino weather phenomenon.

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On July 9, 1979, Voyager 2 made its closest approach to the largest planet in our solar system. Now in interstellar space. Voyager 2 altered some of our ideas about the Jovian system.

The Voyager probes are: humanity's longest running spacecraft as they have been flying since 1977 Both Voyager 2 and Voyager 1 are now in interstellar space, and though their power sources are gradually fading, they are still operational as of now.

It might seem counter-intuitive, but Voyager 2 was the first to be launched on August 20, 1977-about two weeks before the launch of Voyager 1. Both spacecraft were equipped with an extensive array of instruments to gather data. about the outer planets and their systems, in addition to carrying a slow-scan colour TV camera capable of taking images of the planets and their moons.

Based on Mariners

The design of the Voyagers was based on the Mariners and they were even known as Mariner 11 and Mariner 12 until March 7. 1977. It was NASA administrator James Fletcher who announced that the spacecraft would be renamed Younger. The Voyagers are powered by three plutonium dioxide radioisotope thermoelectric generators (RTGS) mounted at the end of a boom (a long metal beam extending from the spacecraft and serving as a structure subsystem).

Even though Voyager 1 was launched a little later, it reached Jupiter first in 1979 as it took a trajectory that put it on a faster path. Voyager 2 began transmitting images of Jupiter from April 24, 1979 for time-lapse movies of atmospheric circulation. For the next three-and-a-half months, until August 5 of that year, the probe continued to click images and collect data. A total of 17,000 images of Jupiter and its system were sent back to the Earth.

The spectacular images of the Jovian system included those of its moons Callisto, Europa, and Ganymede. While Voyager 2 flew by Callisto and Europa at about half the distance between the Earth and its moon, it made an even closer approach to Ganymede.

Ocean worlds

The combined cameras of the two Voyager probes, in fact. covered at least four-fifths of the surfaces of Ganymede and Callisto. This enabled the mapping out of these moons to a resolution of about 5 km.

Voyager 2's work, along with observations made before and after, also helped scientists reveal that each of these moons were indeed an ocean world.

On July 9, 1979, the probe made its closest approach to Jupiter. Voyager 2 came within 6,45,000 km from the planet's surface, less than twice the distance between Earth and its moon. It detected many significant atmospheric changes, including a drift in the Great Red Spot in addition to changes in its shape and colours.

Voyager 2 also relayed photographs of other moons like lo and Amalthea. It even discovered a Jovian satellite, later called Adrastea, and revealed a third component to the planet's rings. The thin rings surrounding Jupiter, as had been seen by Voyager 1 as well, were confirmed by images looking back at the giant planet as the spacecraft departed for Saturn. As the probe used the gravity assist technique, Jupiter served as a springboard for Voyager 2 to get to Saturn.

Studies all four giant planets

 Four decades after its closest approach to Jupiter, Voyager 2 successfully fired up its trajectory correction manoeuvre thrusters on July 8, 2019. These thrusters, which had themselves last been used only in November 1989 during Voyager 2's encounter with Neptune, will be used to control the pointing of the spacecraft in interstellar space.

In those 40 years, Voyager 2 had achieved flybys of Saturn (1981), Uranus (1986), and Neptune (1989), thereby becoming the only spacecraft to study all four giant planets of the solar system at close range. Having entered interstellar space on December 10, 2018, Voyager 2 is now over 132 AU (astronomical unit-distance between Earth and the sun) away from the Earth, still relaying back data from unexplored regions deep in space.

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"In space, no one can hear you scream." You may have heard this saying. It's the tag line from the famous 1979 science fiction movie "Alien." It's a scary thought, but is it true? The simple answer is yes, no one can hear you scream in space because there is no sound or echo in space. I'm a professor of astronomy, which means I study space and how it works. Space is silent – for the most part.

How sound works

To understand why there's no sound in space, first consider how sound works. Sound is a wave of energy that moves through a solid, a liquid or a gas. Sound is a compression wave. The energy created when your vocal cords vibrate slightly compresses the air in your throat, and the compressed energy travels outward.

A good analogy for sound is a slinky toy. If you stretch out a Slinky and push hard on one end, a compression wave travels down the Slinky. When you talk, your vocal cords vibrate. They jostle air molecules in your throat above your vocal cords, which in turn jostle or bump into their neighbours, causing a sound to come out of your mouth.

Sound moves through air the same way it moves through your throat. Air molecules near your mouth bump into their neighbours, which in turn bump into their neighbours, and the sound moves through the air. The sound wave travels quickly, about 1,223 kilometres per hour, which is faster than a commercial jet

 Sound in the solar system

Scientists have wondered how human voices would sound on our nearest neighbouring planets. Venus and Mars. This experiment is hypothetical because Mars is usually below freezing, and its atmosphere is thin. unbreathable carbon dioxide. Venus is even worse - its air is hot enough to melt lead, with a thick carbon dioxide atmosphere.

On Mars, your voice would sound tinny and hollow, like the sound of a piccolo On Venus, the pitch of your voice would be much deeper, like the sound of a booming bass guitar.The reason is the thickness of the atmosphere. On mars the thin air creates a high-pitched sound,and on venus the thick air creates a low-pitched sound. The team that worked this out simulated other solar system sounds, like waterfall on saturn’s moon titan.

Deep space sounds

While space is a good enough vacuum that normal sound can't travel through it, it's actually not a perfect vacuum, and it does have some particles floating through it. Beyond the Earth and its atmosphere, there are five particles in a typical cubic centimetre - the volume of a sugar cube- that are mostly hydrogen atoms.

By contrast, the air you are breathing is 10 billion billion (1019) times more dense. The density goes down with distance from the Sun, and in the space between stars there are 0.1 particles per cubic centimetre. In vast voids between galaxies, it is a million times lower still fantastically empty.

The voids of space are kept very hot by radiation from stars. The very spread-out matter found there is in a physical state called a plasma. A plasma is a gas in which electrons are separated from protons. In a plasma, the physics of sound waves get complicated. Waves travel much faster in this low-density medium, and their wavelength is much longer.

In 2022, NASA released a spectacular example of sound in space. It used X-ray data to make an audible recording that represents the way a massive black hole stirs up plasma in the Perseus galaxy cluster, 250 million light years from Earth. The black hole itself emits no sound, but the diffuse plasma around it carries very long wavelength sound waves.

The natural sound is far too low a frequency for the human ear to hear, 57 octaves below middle C which is the middle note on a piano middle of the range of sound people can hear. But after raising the frequency to the audible range, the result is chilling - it's the sound of a black hole growling in deep space.

Space is a vacuum

So what about in space? Space is a vacuum, which means it contains almost no matter. The word vacuum comes from the Latin word for empty. Sound is carried by atoms and molecules, In space, with no atoms or molecules to carry a sound wave, there's no sound. There's nothing to get in sound's way out in space, but there's nothing to carry it, so it doesn't travel at all. No sound also means no echo. An echo happens when a sound wave hits a hard, flat surface and bounces back in the direction it came from By the way, if you were caught in space outside your spacecraft with no spacesuit, the fact that no one could hear your cry for help is the least of your problems. Any air you still had in your lungs would expand because it was at higher pressure than the vacuum outside. Your lungs would rupture. In a mere 10 to 15 seconds, you'd be unconscious due to a lack of oxygen.

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