We once thought that we were the centre of everything, as shown by Aristotle and Ptolemy, with their geocentric view of the universe. This then eventually developed into Alan Guth's view of an expanding universe, with the knowledge that neither we, nor even the Sun, are in the centre of the universe. Instead, we are getting further away from everything, seen by Hubble's observations of the redshift of the universe [1].
This notion that we aren't the centre of everything has led to a question of "Are we alone?". It has been widely explored in culture, from the martians in 'War of the Worlds', to E.T in 'E.T. the Extra-Terrestrial'. Our views of these illusive creatures have been both hostile and kind, yet we still have the urge to find out if they exist and where they live. Indeed, in a YouGov survey in 2015, when asked if they believe if there is extra-terrestrial intelligent life, 52% of the 1751 people surveyed said yes [2], showing just how embedded into our culture this hope for other life is.
Martians vs. Thunder Child by Henrique Alvim Corrêa
Little Green Men
With missions like the Mars Viking Lander, and projects like SETI (the Search for Extra-Terrestrial Intelligence), we have been scouring the universe to try and find life, or habitable conditions, on other planets and around other stars.
120 years ago, some believed that there was that intelligent life did exist on other worlds, and not only that but on our neighbour, Mars. Observations of the intricate canal system that laced the entirety of Mars to supposedly irrigate the crops on the drying world with water from the frozen ice caps [3]. Some years later, it was deemed from observations from the 1976 Viking Lander Mission that this view was far from the truth, with life looking unlikely in today's world.
However saddening this was, we still had some hope, with searches continuing, like famous discoveries such as LGM-1 (Little Green Man). Jocelyn Bell and her team of scientist at Cambridge University discovered a strange radio signal which was a regular pattern of pulses of radio waves directed at them. They thought that it was possibly aliens, before realising the staggering reality that it was the first detection of a pulsar: a dense ball of spinning gas, with jets of gamma rays (high frequency light) streaming from its poles, being what was picked up by the radio telescope (they were radio waves because of the red shift of the waves from high frequency gamma to low frequency radio) [4].
First radio signal of Pulsar, examined by Jocelyn Bell. Credit: Billthom, CC BY-SA 4.0
'Like a Candy Store for Microbes'
WAIT Hunter (2008) [13]
The solar system, and indeed the universe, appeared to be empty of life apart from us, until we searched on not just planets, but moons: moons like Europa, orbiting Jupiter. This unlikely place was one identified by the Galileo spacecraft as having a salty liquid water ocean locked under the surface, which could harbour life. [5]
Water, being a key component in the search for life, has lead to many more places being identified as possible alien habitats, like Enceladus, orbiting Saturn. This moon was seen by the Cassini spacecraft, which flew through the plumes of vapour spewing from the alien surface. All key components for life were found, from hydrogen to carbon compounds [6]. The only thing is, it's a very long way away!
False colour Cassini image of jets in the southern hemisphere of Enceladus. Credit: NASA
'Is There Intelligent Life on Earth?'
SAGAN C. (1994) Pale Blue Dot. New York: Random House
Looking further still, the SETI Institute is an organisation aimed at finding out: what life is, how does life begin, and if we are alone. They use many tools to fulfil their aims, one of which is the Drake Equation [7]. Formulated by Frank Drake, the equation outlines the parameters that need to be known to find out how many civilisations there are in the Milky Way, who's electromagnetic (light) emissions are detectable. (the equation itself can be found on SETI's website) [8].
The Drake Equation has led to many research projects, from searching for radio signals from other worlds, to searching on Mars to see if life existed or exists still today [8].
Allen Telescope Array, North East of San Francisco in California, USA.
Credit: Colby Gutierrez-Kraybill, CC BY 3.0
'Aerial Life'
[14]
On 14th September, the world found out about our most recent, most surprising and most definite detection yet of alien life. Unlike finding other worlds that look habitable, but are very far away or desolate today, we have found our neighbour, Venus, to possibly support life in the modern day.
Observations, using the James Clerk Maxwell Telescope in Hawaii and ALMA (Atacama Large Millimiter/submillimeter Array) in Chile, have been directed at a little researched gas called phosphine. It is a gas that smells like rotting fish, being given off by sewage and swamps, to name a few sources. It is poisonous to us oxygen breathers, but to the anaerobic (who breathe without oxygen), it is nothing of the sort. What is interesting is that it can easily be destroyed by sunlight and sulphuric acid (both in abundance on Venus), so it must have been recently produced.
The only thing is, there is a reason why scientists have not ventured to look for life there in recent years. This is because of the truly inhospitable conditions, from 90x the atmospheric pressure of Earth, to the sulphuric acid in abundance, with 75-95% of Venus' clouds being this, and 95% of the atmosphere comprised of carbon dioxide, along with a surface temperature at an uncomfortable 400ºC.
However, the theory behind such a discovery as this is that, many years ago, life did exist on the surface of Venus, when the climate was more similar to ours. This life then died out, leaving behind microbial life 50km up in the atmosphere, which live in a ~20ºC climate with surface pressures like Earth, but still with the sulphuric acid and carbon dioxide abundant atmosphere.
It may sound like a far cry from what life on Earth needs, but it still sounds pretty promising. Scientists have tested to see if volcanoes, lightning or chemical reactions in the atmosphere could do the same thing, and they've not found anything yet, leading us to the conclusion that maybe there is life there. The question is, how is it adapted to not get burnt up and dissolved in the atmosphere? [9] [10] [11] [12]
Venus imaged by NASA's Mariner 10 Spacecraft. Credit: NASA
We may never know whether or not there is life somewhere else, but I think that throughout history we have seen examples of our human-centric views being incorrect, with the Earth being at the centre of everything being a key example of that. I feel that this view of Venus not being hospitable may be yet another thing that we see ourselves as the "centre" of, but I'm sure other life in the universe, in the past, present and future, were, are and will think the same.
by George Abraham, ADAS member
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References
"Cosmological Theories through History". Physics of the Universe. Archived from original 19th September 2020.
"YouGov Survey Results". YouGov. Archived from original 19th September 2020.
"Tracing the Canals of Mars". Space.com. Archived from original 19th September 2020.
"Little Green Men?". Space.com. Archived from original 19th September 2020.
"Extraterrestrial Life" ESA. Archived from original 19th September 2020.
"Small Saturn moon has most of conditions needed to sustain life" Guardian. Archived from original 19th September 2020.
"Drake Equation" SETI Institute. Archived from the original 19th September 2020.
"Is there life floating in the clouds of Venus?" BBC News. Archived from the original 17th September 2020.
"'Phosphine gas found in Venus’ atmosphere may be ‘a possible sign of life'". Science News. Archived from the original 20th September 2020.
"Life on Venus". BBC The Sky at Night. Archived from the original 20th September 2020 (the programme is only available to watch in the UK on the BBC website)
"Possible sign of life on Venus stirs up heated debate". National Geographic. Archived from the original 20th September 2020.
"Saturn's moon Enceladus has all the ingredients needed for alien life". Wired. Archived from the original 25th September 2020.
"Extra-Terrestrial “Aerial” Life on Venus?". SciTech Daily. Archived from the original 17th September 2020