While mankind continues exploring the universe hoping to one day finally answer whether we are alone in the universe, various new studies published relatively recently have proposed that life as we know it may have been much more widespread in our solar system than initially thought. According to astronomers, primitive alien life may have existed on Mars (and maybe it still does), Venus, and even Mercury.

Scientists have argued for years that Mars was the most likely place for life to have developed, besides Earth. Although the red planet is now a barren world, in the distant past, millions of years ago, Mars may have had not only an atmosphere but oceans, rivers, and lakes, therefore offering life as we know it a chance on the surface.

But what about planets that are closer to the Sun? What about Mercury and Venus? Recently studies have revealed surprising details about the two closest planets to the Sun.

A study published in 2019 has suggested that billions of years ago, the second-closest planet to the Sun, Venus, may have supported life as we know it. As revealed by scientists, Venus may have had a perfectly habitable environment on its surface for 2 to 3 billion years after the planet’s formation. This means that life as we know it may have had more than enough time to develop there.

The fact that Venus may once have hosted life may not be so surprising. In fact, back in 1978, NASA’s Pioneer Spacecraft found conclusive evidence that Venus may have had shallow oceans on its surface. Since then, a number of missions that have studied the planet atmosphere have found that the planet transitioned from an Earth-like world to the hellish, desolate place it is today.

Scientists believe that Venus may have been a planet similar to Earth, with a temperate climate that allowed ample amounts of liquid water to exist on its surface for 2 to 3 billion years. Then, suddenly, a cataclysmic event occurred some 700 million years ago, triggering a runaway greenhouse effect which caused the atmosphere of the planet to shift and become extremely dense and hot.

In addition to Venus, the closest planet to the Sun, Mercury, may also have developed the necessary conditions for life to survive.

According to scientists, it is possible that certain parts of Mercury’s subsoil, and those of similar planets in the galaxy, may have once been able to foster prebiotic chemistry, and perhaps even simple life forms, according to a study by the Planetary Science Institute.

“The findings mean that Mercury had a thick volatile-rich—possibly but not necessarily water-rich—crust in this location,” explained Planetary Science Institute Research Scientist and lead author of the study, Alexis Rodriguez.

“Mercury’s surface temperature reaches a scorching 430 degrees Celsius during the daytime, and in the absence of an atmosphere, it plummets to -180 degrees Celsius at night. So, its surface environments have rightfully been out of scientific consideration as a possible host of life. However, the paper raises the prospect that some subsurface regions of Mercury have shown a capacity for hosting life,” Rodriguez added.