Happy Pi Day! From Mars landing to exploring new planets, here’s how Pi helps NASA

© Provided by The Indian Express Mars, Ingennuity helicopter, perseverance rover In an image provided by NASA/JPL-Caltech shows the Mars helicopter Ingenuity showing the backshell of Perseverance’s landing capsule, its supersonic parachute and the related debris field on April 19, 2022.

March 14. 3/14 if you use the American date system. It is Pi day, one of the few days of the year when mathematicians and the scientists who practice it are celebrated. But did you know how NASA, the American space agency, uses Pi in its everyday work?

Pi, or π, is the mathematical constant that is used to denote the ratio between a circle’s circumference (the length of its border if it was a straight line, essentially) to its diameter (the length of the longest line that can pass through its centre, ending at its border.

The approximate value of Pi is 3.14. This is why March 14 is celebrated as the day commemorating one of the most well-known symbols in mathematics. To demonstrate its importance to science, NASA has published a list of the many ways in which it uses the symbol in its work. Here are some of them.

© Provided by The Indian Express GJ 367b This illustration shows anexoplanet called GJ 367b, that is located roughly 31 light years from Earth and orbits its star in only about 8 hours, with a density greater than our planet’s and an internal structure similar to that of Mercury. (SPP 1992/Patricia Klein/Handout via REUTERS) (Illustrative image)

Mapping unknown worlds

Ancient explorers of the Earth, like Columbus and others, made maps as they visited different countries and land masses. Just like that, when spacecraft visit other planets, they make maps that document the processes on the planet, like how water flows around the globe.

These maps are made by spacecraft as they orbit other planets. But they have cameras that have rectangular fields of view, which capture images in “bands” on the planet’s surface. To figre out how many images it will take to map an entire planet, scientists use a formula that includes Pi.

Finding new worlds

Pi is not just useful when you reach a planet and map, scientists need it to search for distant planets as well. Powerful telescopes in space and on Earth track how much light is emitted by distant stars. When an exoplanet (a planet outside our solar system) passes by a star, the telescope will detect a dip in the amount of light emitted by the star.

Scientists will use this percentage figure and the formula for the area of a circle to derive the size of the planet that passed in front of the star.

© Provided by The Indian Express An artist’s illustration of Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star, is seen in this undated handout picture released by NASA. (Reuters) (Illustrative image)

Finding planets which could harbour life

After discovering new exoplanets, one of the most interesting questions is whether those planets can support life as we know it. If they can, they are referred to as “potentially habitable”. It probably comes as no surprise, but scientists use Pi to understand whether exoplanets are habitable.

For a planet to be habitable, it needs to be in a “Goldilocks zone,” where it is neither too far from the star it is orbiting nor too close. It needs to receive the right amount of heat for life to happen, but too much heat can stop it altogether. Scientists use pi to find out the inner and outer edges of the goldilocks zone around a particular star.

After that, they use Pi and Kepler’s third law to calculate how long a particular exoplanet takes to make one full orbit of a star, which will reveal the planet’s location and whether it is in the Goldilocks zone.

Parachuting on Mars

Now that you know how scientists use Pi to learn more about other planets, what if they want to land on one? Pi is yet again helpful here. NASA scientists use Pi to land rovers and landers on Mars.

According to the space agency, no Mars landing is exactly the same, but they all have one thing in common: parachutes. When you drop something on to the Martian surface, it is imperative that the object is slowed down with the help of the thin Martian atmosphere.

When designing the parachutes that can do this, engineers have to take into account all sorts of things, from the mass and velocity of the spacecraft to the elevation of the landing site and the density of the atmosphere. Pi helps them decide how big the parachute needs to be so that it can generate enough drag to slow down an object’s descent.

© Provided by The Indian Express Green comet An exceptionally bright “green comet” was visible in the night sky earlier this year. (Image credit: Dan Bartlett, NASA)

Tracking asteroids and comets

It is not just planets that can be explored using Pi, but even asteroids and comets too! Scientists at NASA’s Center for Near-Earth objects are tasked with the job of determining how fast asteroids and comets are rotating, among other things.

Based on observations made from Earth, scientists can estimate how long it takes an object to make one complete rotation on its axis. Using this figure and formula with pi, scientists can estimate the angular velocity of the object in question, whether it is an asteroid or comet.