Earth is a remarkable planet that hosts all kinds of life. From glistening oceans with marvelous sea creatures to steamy rainforests with diverse wildlife, there are always new ways of life and living being discovered. With all of these complexities, one might begin to wonder: How did life form on Earth? Scientists have worked endlessly to answer this question, through the creation of many different hypotheses. However, before diving into these proposed answers, let’s first go over what is needed for life to exist.
What is Needed for Life?
There are three essential ingredients scientists say are required for life to form as we know it on Earth: organic molecules – including carbon, alongside hydrogen and others, a source of energy, and liquid water. Starting off with chemistry, all life is composed of organic compounds which contain the element carbon plus nitrogen and oxygen, to name a few. Next, life requires liquids such as water. This is because liquids allow the organic compounds to mix with one another, resulting in increased complexity. Lastly, life needs energy – for Earth, this is in the form of the sun. This energy charges up the chemical reactions that are needed for all of life. Earth initially had two of these ingredients: water and energy; however, Mother Nature was lacking organic molecules and compounds.
How did these molecules get to Earth?
So then, how did life form on Earth if there were no chemical compounds originally here? Although there are several theories, we’ll be concentrating on one of the main hypotheses regarding this question: the panspermia hypothesis, or the “life seed” hypothesis. This hypothesis theorizes that life was brought to Earth by a physical object from outer space, like an asteroid or meteor. It suggests that a piece of a life-bearing planet broke off, and eventually landed on Earth, giving Earth the materials it needs for life. The idea that organic molecules could be foreign to Earth is compelling, and recent analyses done on an asteroid collected by NASA might be an essential asset in supporting this theory.
Bennu the Asteroid
Bennu, as named by NASA, is an asteroid that comes close to Earth about every six years, and is thought to have broken off from a larger, carbon-rich asteroid anywhere between 700 million to 2 billion years ago. In 2020, NASA led a mission to collect rock from Bennu, through a project known as The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer mission (OSIRIS-REx). Three years later, this mission retrieved a 4.3 ounce sample of Bennu that was delivered back to Earth in pristine condition. Through lab analyses of this fragment, remarkable organic compounds were found. Firstly, diverse chemical and organic compounds that are needed to make proteins were found. Proteins are incredibly crucial in the structure and function of living organisms. Secondly, all five nucleotides that make up RNA and DNA were found. RNA and DNA are the basic ‘building blocks’ of life! Lastly, minerals that form when salty water is present were also collected–showcasing that Bennu also possessed liquids, another important precondition for life.
While these factors alone do not prove that there was definitely life on Bennu or the planet where it stemmed from, scientists believe that this evidence could bring us a step closer to uncovering how chemical compounds like these came to Earth. Hopefully, with continued research, there will be more incredible discoveries that will help us understand how life on Earth started.
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