World UFO Day 2020: How close have we actually got to finding aliens, and what would they be like?

Exciting data has emerged from Mars and Enceladus, but extra-terrestrials will likely be tiny bacteria not intergalactic space travellers

As another World UFO Day comes around, many will welcome the opportunity to muse about advanced alien life forms jetting across the universe in bizarre spacecraft.

While the existence of UFOs is not a conventional topic of scientific research, there is no shortage of scientists searching for extra-terrestrial life.

In recent years, exciting announcements have emerged from the world’s biggest space agencies that have provided some of the most tantalising hints yet that alien life may be lurking in our own solar system.

Data gathered by Nasa’s Curiosity rover allowed scientists to identify evidence of ancient organic matter on the surface of Mars. These “ingredients for life” suggest the red planet may not have always been as lifeless as it is today.

Meanwhile, the moons Enceladus and Europa have been singled out as potential targets in the search for alien life due to the deep oceans that cover their surface.

Scientists also announced they were “blown away” by the discovery of large organic molecules on Enceladus, which orbits the gas giant Saturn.

The discovery suggests that to the best of our knowledge this distant moon is the only body besides Earth to “simultaneously satisfy all of the basic requirements for life as we know it”.

However, the life being discussed is a long way from building and operating its own spacecraft.

Aliens in films and literature are often presented as large, malevolent and far more technologically advanced than humanity.

The late, great Stephen Hawking was known to make pronouncements about these kinds of aliens, warning on several occasions about the dangers of encountering such cosmic travellers.

He even compared the meeting between humans and aliens to the meeting of Native Americans and Christopher Columbus, which in his words “didn’t turn out so well”.

One University of Oxford team applied evolutionary theory to "make predictions that are independent of Earth's details", and concluded that actually, aliens are likely to look something like us.

In practice, however, experts think the most likely alien life forms we will come across are going to be some kind of alien microbes.

For the first 2.9 billion of the 3.5 billion years life has existed on Earth, it consisted of tiny, single-celled creatures. Modern humans have only existed for around 300,000 years.

This means the likelihood of finding a planet that not only supports life but is home to complex life like us is incredibly slim.

Astrobiology is the name given to the branch of science that deals with the hypothetical origins and evolution of life beyond planet Earth. Many of its proponents tend to focus on bacteria that inhabit the planet’s most extreme enviroments – reasoning that Earth’s coldest, hottest or most acidic regions are reasonable proxies for the conditions found on distant planets and moons.

Now that promising signals have been uncovered in relatively close proximity to Earth, scientists are using their knowledge of life on Earth to guide their search for aliens.

Missions such as the ExoMars launch and potential future exploration of Enceladus could build on the findings of recent months, and maybe even the first concrete evidence of extra-terrestrial life.

This article was first published on 2 July 2018