Are We Alone in the Universe?

By Amelia Dunlop Year 10

For over 50 years, scientists and astronomers have been trying to search the universe for any signs of extraterrestrial life outside Earth. Currently, Earth is the only known planet in the universe to host life forms, but with the help of advancing technology and research, scientists are slowly discovering more answers of whether we really are alone in the universe.

The Habitable Zone

In order for any life to exist, an exoplanet must be inside the habitable zone (or Goldilocks Zone) - the area around a star in which liquid water can be maintained on the surface of a rocky planet. The exoplanet must also have an atmosphere with the correct percentage and ratio of gases in the air for life to be sustained. To estimate whether a planet falls within the habitable zone, astronomers determine the distance between the exoplanet and the star, and the star’s size and energy output. Earth is within the habitable zone in our solar system, Venus being slightly within the inner edge and Mars being near the outer boundary. Exoplanets that orbit stars in other solar systems are sometimes too far away to determine if they have an atmosphere or whether the conditions allow them to support life. According to the Habitable Exoplanets Catalogue in March 2018, 53 exoplanets could have the capability to support and sustain life, and 13 of those exoplanets could have the potential to be habitable. Recently discovered rocky exoplanets Proxima Centauri b and c, and TRAPPIST-1 e, f and g, are all within the habitable zone of their red dwarf star and their size and position in their solar system resemble that of Earth’s.

Fermi Paradox

The Fermi Paradox refers to the contrast between the high probability that intelligent extraterrestrial life exists, and the absence of evidence of such life. It was first described by Sir Arthur C. Clarke (the late British Sci-Fi author), who stated: "Two possibilities exist: Either we are alone in the universe or we are not. Both are equally terrifying. " Many doubt the fact that there are other life forms in the universe: if there really is intelligent life, why have we not heard from any? In December 2020, an unexplained radio signal was reported from the direction of the star Proxima Centauri: some believe this to be signs from other civilisations - especially as there is a potentially habitable exoplanet orbiting that star - but it most likely that the signal originates from humans or other natural causes...

The Drake Equation

In 1961, Frank Drake created the Drake Equation, to help find out whether there are other intelligent life forms in the galaxy and the amount of them. It calculates the odds of life and communicating civilisations in the Milky Way by multiplying several variables. The challenge for astronomers is to find numbers and values to fill the variables, so the output of the equation is usually only a rough approximation. The more evidence of life in the solar system, the more useful this equation will be to scientists in figuring out how many intelligent life civilizations are actually in the Milky Way. In the 1960’s Drake also conducted a search to scan the skies for artificial radio signals (this was named Project Ozma). With more research into certain exoplanets, their properties and space exploration, scientists may be able to either find other life or discover why we (on Earth) are the only life forms in the whole universe. It is more likely that one day non-intelligent life will be discovered, or new microbial life which could evolve over millions of years.

Sources

● theguardian.com/science/2013/sep/01/20-big-questions-in-science ● space.com/25219-drake-equation.html ● exoplanets.nasa.gov/news/1675/life-in-the-universe-what-are-the-odds/ ● astronomy.com/news/2020/11/the-lonely-universe-is-life-on-earth-just-a-lucky-fluke ● nationalgeographic.com/science/article/alien-hunters-detect-mysterious-radio-signal-from-nearby-star ● livescience.com/fermi-paradox

By Maia Roman Year 10

When Earth was formed, it was: not too hot; not too cold; not too wet; and not too dry.

This meant that liquid water could exist on the surface. Early on, Earth was most likely volcanic forming island arcs as well as dips in the ocean. Places such as ponds or lakes in these volcanic areas are believed to be the environments that kindled the first life on Earth.. Many scientists have theorised that RNA was the first molecule on Earth to self-replicate and begin some form of evolution that led to more and more advanced forms of life, including human beings.

So what is RNA?

There are two types of "nucleic acids" : deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). RNA converts genetic information from DNA to proteins and is located in every cell. DNA is first copied onto a strand of messenger RNA (mRNA) during a process called transcription. Then, the code on the mRNA is "read" and used to create a protein during a process called translation. Translation is broken down into three stages: Initiation, Elongation and Termination. 1. In Initiation the ribosome, mRNA and first transfer RNA (tRNA) all link together. 2. Next, in Elongation, amino acids are transferred to the ribosome by tRNA and are added to the growing protein.

3. Finally, in Termination, a stop codon is reached, and the complex separates and releases the newly formed protein. A codon is a sequence of three nucleotides in mRNA that codes for one amino acid, therefore a stop codon is a codon that signals the end of the translation process of the protein. These two processes are effectively summed up by the central dogma of molecular biology:

DNA → RNA → Protein.

In the 1950s, the Miller-Urey experiment, which experimented on a mixture of water and simple chemicals with electric pulses (mimicking the impact of lightning), proved that amino acids are easy to make. (In case you’re wondering, amino acids are the very building blocks of proteins.) However, other molecules of life are actually harder to synthesise than we imagined, the central reason being the incredible versatility of RNA. Not only can it act like an enzyme, but RNA can also store and transmit information. The catalytic activity of the RNA component in the ribosome synthesises all protein in all organisms. This is what scientists say suggests that RNA dominated an early stage in the evolution of life. So how did the first RNA and DNA molecules form? When I was researching I found that a man named Nicholas Hud, a Georgia tech chemist, and his team say that they have discovered that “the molecule ethidium can assist short polymers of nucleic acids, known as

oligonucleotides, in forming longer polymers. Ethidium can also select the structure of the base pairs that hold together two strands of DNA. " As it grew, the two ends of the growing polymer often reacted with each other as opposed to forming longer chains. This faced the team with quite a challenge known as strand cyclization. Fortunately, Hud and his research team discovered that if they could use a molecule to secure in between two base pairs of DNA, called an intercalator, they could bring short pieces of DNA and RNA together. This way, they could create much longer molecules. The team’s conclusion from the problem they faced was that "if you have the intercalator present, you can get polymers” , but “with no intercalator, it doesn't work” . Apparently “it's that simple. Midwife molecules are believed to be the molecular "midwives" that help “give birth” to RNA. This team tested how much influence a midwife molecule had on creating the Watson-Crick base pairs that make up the structure of DNA. To clarify, the essential rule of the Watson-Crick base pairing system is that Adenine binds to Thymine and Cytosine binds to Guanine, forming base-pairs through hydrogen bonding. Their findings were that the matching base pair was dependent on the midwife present during the reaction and that Ethidium was the most helpful for synthesising polymers with the specific Watson-Crick base pairs of DNA.

Hud’s conclusion was that “the midwife molecules we used had a direct effect on the kind of base pairs that formed. ” "We're not saying that ethidium was the original midwife, but we' ve shown that the principle of a small molecule working as a midwife is sound. " So in conclusion of Hud’s conclusion, although it is not absolutely 100% scientists have found how life on Earth was created.

Sources

● How Did Life Begin? | NSF - National Science

Foundation. 2022. How Did Life Begin? | NSF -

National Science Foundation. [ONLINE] Available at: nsf.gov/discoveries/dis ● c_summ.jsp?cntn_id=117380&org=NSF. [Accessed 10 February 2022]. ● Nature. 2022. How Did Life Begin?. [ONLINE]

Available at: nature.com/articles/d41586-018-05098-w. [Accessed 10 February 2022]. ● Pressbooks. 2022. 5.7 Protein Synthesis – Human

Biology. [ONLINE] Available at: humanbiology.pressbooks.tru.ca/chapter/5-6-prot ein-synthesis/. [Accessed 10 February 2022]. ● Molecular ‘Midwives’ Helped Give Birth to RNA |

News | Astrobiology . 2022. Molecular ‘Midwives’

Helped Give Birth to RNA | News | Astrobiology . [ONLINE] Available at: astrobiology.nasa.gov/news/molecular-midwiveshelped-give-birth-to-rna/. [Accessed 10 February 2022]publications.