Read the text and put the sentences below into the gaps. There is one extra sentence you do not need to use.
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Life from other worlds
How life originated on Earth is one of the most fundamental problems ever to puzzle scientists. The world we know is teeming with remarkable species. It's the existence of these species that separates our planet from all the other worlds we've discovered and explored. Earth's ability to support life has created diverse ecosystems and brought us all into existence. [ ]
Panspermia is the name of one popular theory, stating that life isn't confined to just one planet. The concept of this theory began in a basic form in the work of researchers such as Jöns Jacob Berzelius, Hermann Richter, and Svante Arrhenius from the 1830s through to the early 1900s. According to it, life didn't necessarily originate on Earth, and it can be transported and spread throughout space. [ ] The most convincing and plausible of this theory's explanations for the interplanetary distribution of life is that bacterial colonies were transported from one planet to the next. Evidence of microbial life within meteorites on Earth may indicate that this transportation was made possible by material removed from other bodies that then travelled on its own through space. [ ] Or could microbes have created a series of Earth-like civilisations on numerous planets throughout the universe?
Some versions of the panspermia theory are becoming closer to being either proven or dismissed. As we explore the universe that surrounds our home planet, our evolving knowledge and technology are allowing us to go farther afield and investigate more thoroughly, analysing the facts that weren't paid much attention to before. In some instances, signs of life are being detected on planets that we once thought were lifeless. But it's only when we understand the definition of life more thoroughly that we can begin to truly understand where it came from, along with our own existence.
Although the panspermia theory involves some wild claims that border on science fiction, others are based on fragments of solid scientific evidence.
Some people don't support this theory and believe that life didn't reach Earth from other planets, but was sent here by technologically advanced civilisations.
But its origin happens to be one of the longest-standing debates in scientific history.
If this is the case, is our world a one-off, produced unintentionally?