Is there life on other planets? One of the oldest and most popular question everyone asks whenever a discussion happen around astronomy. Although we generally focus on discussing about possibility of extra-terrestrial intelligent life, finding just ‘life’ or just their traces (like fossils), is more realistic in near future. Discovering alien fossils or martian microbial lifeforms deep inside polar capes of Mars is certainly more probable then Curiosity encountering a bipedal green martian.
What is life?
Wikipedia defines life as – a characteristic that distinguishes physical entities that have biological processes, such as signaling and self sustaining processes, from those that do not, either because such functions have ceased or because they never had such functions and are classified as inanimate. Various forms of life exit, such as plants, animals, fungi and bacteria.
As our understanding of ‘life’ singularly depends upon various ‘known’ life-forms found on Earth, can we even recognize a life-form that’s alien to us?
In our search for life on other planets, we might encounter a certain life-form which might not appear to us as a living entity. One interesting example of such life-form which is occasionally mistaken for non-living things are Corals.
Once we have defined ‘life’, we should move on how and where to find one?
Complex life such as animals, plants etc. take much time to evolve. Best bet would be on microbial – they are one of the first to be formed and some of them can also survive in harsh conditions – which are quite common to be found in the universe.
Yellowstone National Park’s Grand Prismatic Spring contains various populations of heat-loving microorganisms that thrive in the high-temperature water.
Here are some major progress in recent years, in our search for life on other planets:
Search for Biosignatures
Mysterious life forms discovered in centuries-old Hawaiian lava caves where the conditions are like those you will encounter on Mars or other distant planets.
If microbes can survive on these century old lava caves, we might discover them on Mars as well!
Biosignature is any substance that provides scientific evidence of past or present life. A biosignature can provide evidence for living organisms outside the Earth and can be directly or indirectly detected by searching for their unique byproducts.
Search for biosignatures from Earth based telescopes: James Webb Space Telescope is designed in part to investigate exoplanets like gas giants and super Earths, by observing distant planet’s reflected light to detect the signatures possible life.
Discovery of phosphine in atmosphere of Venus: In 2020, scientists detected phosphine in atmosphere of Venus. Phosphine is produced by bacteria thriving in oxygen-starved environments, indicating that microbes could inhabit the planet. Venus is very similar in size and structure to Earth, although much hotter at 471 degrees Celsius and covered in toxic gas.
Cassini detected traces of methane in Enceladus’s plumes: An earthbound microbe, called methanogenic archaeon, survives without oxygen by combining hydrogen and carbon dioxide (both observed in Enceladus’s atmosphere) and emitting methane as a waste product.
Search for Extra-terrestrial Fossils
On the Red Planet, NASA’s Mars rover Perseverance is searching for fossils and traces of aliens in Jezero Crater, an ancient lake bed thought to have once been habitable for microbial life. Perseverance is tasked with searching for signs that microbial life may have lived on Mars billions of years ago. It will collect rock core samples and future missions would return these samples to Earth for further study.
Microbial fossil in a Martian meteorite: In 1996, a team of scientists led by David McKay of NASA’s Johnson Space Flight Center announced that they had discovered evidence for microscopic fossil life in a meteorite from Mars. Martian meteorite ALH84001, recovered in Antarctica. Some scientists have suggested that physical and chemical features in this meteorite provide evidence for microscopic fossil life on Mars.
Conclusion
Microorganisms could exist beyond Earth, and there are plans to search for signs of them on Mars and some of Saturn and Jupiter’s moons. Such organisms might be based on different amino acids (key building blocks of all life) than lifeforms on Earth. It is certain that our first contact is not going to be exciting one.
~AK
References:
Case Study: Fossil Microbes on Mars?
Glacier ice archives nearly 15,000-year-old microbes and phages
Searching for Life in NASA’s Perseverance Mars Samples
Hardy Microbes Hint at Possibilities for Extraterrestrial Life
Scientists have discovered potential signs of life on Venus
