These days, the possibility of finding life “out there” is an integral part of astronomy. The exploration of mars has been spurred in large part by  the search for life or at least conditions that could support it. Extraterrestrial life is hypothetical life that may occur outside Earth and which did not originate on Earth. Such life might range from simple prokaryotes (or comparable life forms) to intelligent beings and even sapient beings, possibly bringing forth civilizations that might be far more advanced than humanity. Given the size of the universe – there are at least 100 billion stars in our home galaxy alone and perhaps 100 billion galaxies of much the same size scattered throughout deep space – few scientists believe that the Earth is the only home of life. But until quite recently, the field of exobiology – the study of extraterrestrial life also known as astrobiology – was almost moribund. It could come up with some interesting speculations but that was about all. The Drake equation speculates about the existence of sapient life elsewhere in the universe.

The Drake Equation:

Astronomer Frank Drake (1930–), who was doing radio astronomy searches for signals from alien civilizations in the early 1960s, came up with an equation that can help estimate how many civilizations could be in the galaxy. His equation looks like this:

N = R* • f_p • n_e • f_L • f_i • f_c • L

where N is the number of civilizations in our galaxy that have the ability to communicate with us. To get to N, you have to multiply the following factors: 

R*—the average star formation in our galaxy each year

f_p —the number of those stars that have planets

n_e —the number of planets that could potentially support life (for each star that has planets) 

f_L —the number of those planets that actually go on to develop some kind of life

f_i—the number of planets that actually do develop intelligent life 

f_c—the number of civilizations that are technologically advanced enough to advertise their existence (through radio signals, etc.) 

L—the length of time it takes for those civilizations to start releasing their “I’m here” signals

Necessities for life

The most vital ‘exobiology’ discoveries, though, were made right here on Earth. Biologists have learned that life is much more robust than most scientists believed 30 years ago. Earth microorganisms have been found thriving in astonishingly hostile environments. Deep beneath the oceans, for example, near the volcanic vents known as black smokers, some microbes grow and multiply at temperatures above 110 degrees – according to some scientists, perhaps as high as 170 degrees. 

Others thrive in acid conditions that would strip the skin from a human, while others still make a comfortable living in hot rocks kilometres below the ground. Some even prefer cold to heat: Antarctic life-forms can manage very well in what amounts to a permanent deep-freeze.

The existence of these so-called extremophile organisms radically changed our view of what might be called “the necessities of life”. Extremophiles live happily without sunshine, without moderate warmth, without organic molecules to feed off and with no need for photosynthesis – many digest raw minerals and fuel themselves with basic chemical reactions.

The Kepler Mission

The Kepler mission is on the hunt for Earth-like planets around other stars, called exoplanets, and has found many planet candidates, not all of them suitable for life as we know it. Astronomers using the European Southern Observatory in Chile have even found an Earth-sized planet circling around Alpha Centauri B, which lies 4.37 light-years from Earth. While the newly discovered planet is too hot and close to its star to be hospitable to life, the discovery is another step towards finding life elsewhere.

I am sure that in the distant future we will find life elsewhere. The chances of ET being highly advanced or dangerous human eaters, is very very low. Most probably they will be some microscopic organisms(sorry to disappoint you). But, do not let this stop you from imagining.

https://en.wikipedia.org/wiki/Extraterrestrial_life https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/Extraterrestrial_life