The mysteries of space have confounded and astounded humankind throughout history.
The relentless search for answers to the secrets in the skies has inspired the world to put feet on the Moon and continue to embark on journeys into space to deepen our understanding of the universe around us.
The thirst for knowledge was further fuelled by sightings of flying objects and what appeared to be messages from other galaxies.
Earlier this week, China claimed to have received mysterious signals from what could be an “alien civilisation”, but then deleted the report.
Recently, Nasa formed an independent team of researchers that will study sightings of unidentified aerial phenomena, a term now used by the space agency to refer to UFOs (unidentified flying objects).
Thousands of UFO reports are filed each year from people around the world, although Nasa has never referred to any of these sightings as “aliens”.
Scientists say these sightings often have a simple explanation. But for some, incidents are still an enigma.
The National lists five of the strangest space mysteries reported over the years.
Unidentified object flies past SpaceX crew capsule
Last year, an unidentified object flew dangerously close to a SpaceX Crew Capsule.
The object streaked past the spacecraft only minutes after it had separated from its Falcon 9 rocket booster.
The unusual event was caught on camera and took the internet by storm, with many users spooked by the incident.
Some experts said it must have been ice from liquid oxygen in the rocket, but neither SpaceX or Nasa confirmed this assertion.
Minutes before the object flew past their capsule, astronauts on the spacecraft were asked to put their suits on immediately and secure themselves into their seats.
China receives signals from 'alien civilisation'
Earlier this week, China said its enormous Sky Eye telescope may have received signals from “alien civilisations”.
A report was published by China’s Science and Technology Daily on June 14, which was later deleted without explanation.
But the news quickly went viral and was trending on Twitter, with news organisations around the world reporting the findings.
The signals were picked up by China’s Aperture Spherical Radio Telescope, also called Sky Eye, the largest radio telescope in the world.
It has been searching for extraterrestrial life since 2019 by scanning for radio signals in deep space.
Zhang Tongjie, head scientist at China Extraterrestrial Civilisation Research Group, said that the signals could have been some kind of radio interference, and that more research was needed.
A ‘doorway’ on Mars?
Last month, social media was abuzz with news that a Nasa rover had found an “alien door” on Mars.
Some of the pictures that were circulating online were very convincing, but they were zoomed in significantly, which made the “door” appear larger than it is.
Experts said the formation was a narrow, naturally occurring crevice in the rocky, barren terrain, according to AP.
The images were taken by the Curiosity rover, which was investigating a region on Mount Sharp on Mars, an area that could hold further evidence that shows the planet was once wet and then dried out.
Nasa’s Perseverance rover, which landed on Mars last year, is searching for signs of ancient life.
‘Mystery hut' on the Moon
Earlier this year, images of a “mystery hut” on the Moon’s far side went viral.
They were taken by China’s Yutu 2, a robotic lunar rover that landed on the Moon in early 2019.
The structure certainly had a strange shape and baffled many social media users.
But after driving for two weeks, the rover got close enough to the mystery object to take clearer images of it.
Turns out it was only a rabbit-shaped rock.
The rover’s team described it as a ‘jade rabbit’, a figure from Chinese mythology that lives on the Moon.
Mysterious radio signals from centre of our galaxy
Last year, scientists were puzzled after unknown radio signals were being received from the centre of the Milky Way.
There were several signals recorded in the past year, but astronomers were unable to find the source.
A study in the Nature Journal suggests that they could have been coming from hidden planets.