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Humans on Earth are here thanks to a planet smashing into Earth billions of years ago, scientists say.
The same collision – which happened 4.4 billion years ago – formed the moon, according to a new paper.
As well as shedding light on how life came to form on our own planet, the discovery has important consequences for our search for life elsewhere in the universe, the scientists say.
According to the "giant impact hypothesis", the moon was created from debris left behind when the Earth and a body the size of Mars smashed together.
The new theory proposes that the cosmic crash delivered most of the volatile elements essential for life to the Earth.
The "donor" planet was an embryonic world with a sulphur-rich core.
Show all 30 1 /30Nasa's most stunning pictures of space Nasa's most stunning pictures of space Solar Flare An image from Nasa's Solar Dynamics Observatory (SDO) shows a 200,000 mile long solar filament ripping through the Sun's corona in September 2013
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Nasa's most stunning pictures of space Nasa Celebrates 50 Years of Spacewalking For 50 years, NASA has been "suiting up" for spacewalking. In this 1984 photograph of the first untethered spacewalk, NASA astronaut Bruce McCandless is in the midst of the first "field" tryout of a nitrogen-propelled backpack device called the Manned Maneuvering Unit (MMU)
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Nasa's most stunning pictures of space A Hubble Cosmic Couple The spectacular cosmic pairing of the star Hen 2-427 — more commonly known as WR 124 — and the nebula M1-67 which surrounds it
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Nasa's most stunning pictures of space Earth from the ISS From the International Space Station, Expedition 42 Flight Engineer Terry W. Virts took this photograph of the Gulf of Mexico and U.S. Gulf Coast at sunset
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Nasa's most stunning pictures of space NuSTAR X-rays stream off the sun in this image showing observations from by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, overlaid on a picture taken by NASA's Solar Dynamics Observatory (SDO)
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Nasa's most stunning pictures of space Cassiopeia A c A false colour image of Cassiopeia A comprised with data from the Spitzer and Hubble Space Telescopes and the Chandra X-Ray observatory
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Nasa's most stunning pictures of space Earth Observations From Gemini IV in 1965 This photograph of the Florida Straits and Grand Bahama Bank was taken during the Gemini IV mission during orbit no. 19 in 1965. The Gemini IV crew conducted scientific experiments, including photography of Earth's weather and terrain, for the remainder of their four-day mission following Ed White's historic spacewalk on June 3
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Nasa's most stunning pictures of space Yellowstone from space NASA astronaut Reid Wiseman shared this image of Yellowstone via his twitter account
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Nasa's most stunning pictures of space Solar Flare An X1.6 class solar flare flashes in the middle of the sun in this image taken 10 September, captured by NASA's Solar Dynamics Observatory
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Nasa's most stunning pictures of space Mars Rover Spirit Nasa's Mars Rover Spirit took the first picture from Spirit since problems with communications began a week earlier. The image shows the robotic arm extended to the rock called Adirondack
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Nasa's most stunning pictures of space Morning Aurora From the Space Station Nasa astronaut Scott Kelly captured this photograph of the green lights of the aurora from the International Space Station
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ESA/Hubble & NASA
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Nasa's most stunning pictures of space Hubble Peers into the Most Crowded Place in the Milky Way This Nasa Hubble Space Telescope image presents the Arches Cluster, the densest known star cluster in the Milky Way
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Nasa's most stunning pictures of space An Astronaut's View from Space Nasa astronaut Reid Wiseman tweeted this photo from the International Space Station on 2 September 2014
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Nasa's most stunning pictures of space Expedition 39 Landing A sokol suit helmet can be seen against the window of the Soyuz TMA-11M capsule shortly after the spacecraft landed with Expedition 39 Commander Koichi Wakata of the Japan Aerospace Exploration Agency (JAXA), Soyuz Commander Mikhail Tyurin of Roscosmos, and Flight Engineer Rick Mastracchio of NASA near the town of Zhezkazgan, Kazakhstan
(NASA/Bill Ingalls)
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Laboratory experiments and computer simulations suggested that debris from the destroyed planet deposited the life elements on Earth.
They included most of the nitrogen and carbon found in living things, including humans alive today.
Lead scientist Rajdeep Dasgupta, from Rice University in Texas, said: "From the study of primitive meteorites, scientists have long known that Earth and other rocky planets in the inner solar system are volatile-depleted.
"But the timing and mechanism of volatile delivery has been hotly debated. Ours is the first scenario that can explain the timing and delivery in a way that is consistent with all the geochemical evidence."
Dr Dasgupta said the study could allow humanity to understand more about how the ingredients for life might form on other rocky planets like our own.
"This study suggests that a rocky, Earth-like planet gets more chances to acquire life-essential elements if it forms and grows from giant impacts with planets that have sampled different building blocks, perhaps from different parts of a protoplanetary disk."
The research is published in the journal Science Advances.
Additional reporting by Press Association
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