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Asteroid hidden behind Mars could be Moon’s long-lost twin

Charlotte Edwards, November 8, 2020 7:00PM The Sun

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An asteroid sharing the orbit of Mars could be a long-lost piece of the moon, broken off in a cosmic collision. media_cameraAn asteroid sharing the orbit of Mars could be a long-lost piece of the moon, broken off in a cosmic collision.


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A huge asteroid that’s following Mars’s orbit could be our Moon’s long-lost twin.

This is according to scientists who say the space rock has an identical composition* to some parts of the lunar surface.

The researchers think asteroid (101429) 1998 VF31 could be a “relic* fragment of the Moon’s original solid crust”.

Scientists used a tool called a spectrograph on the European Southern Observatory’s 8m Very Large Telescope (or VLT) in Chile to observe the asteroid.

It allowed them to see how sunlight reflected from it and then they compared it to the Moon.

“The spectrum* of this particular asteroid seems to be almost a dead-ringer* for parts of the Moon where there is exposed bedrock such as crater interiors and mountains,” explained Galin Borisov, an astrochemist from the Armagh Observatory and Planetarium in Northern Ireland.

ASTEROID on a collision course with Planet Mars. media_cameraTrojan asteroids share the orbit of planets, including Jupiter, Mars and Earth.

We don’t know for sure why that is, but one theory is that the Moon and the asteroid have a similar origin or were once combined and then broke apart.

The asteroid is part of a group of Trojan asteroids sharing the orbit of Mars.

Trojans are celestial* objects that share a planet’s orbit around the sun. Most of the Trojan asteroids we know about share Jupiter’s orbit, but other planets have them too, including Mars and Earth.

Astronomer Apostolos Christou said the early Solar System was “very different from the place we see today”.

“The space between the newly-formed planets was full of debris* and collisions were commonplace,” he said.

“Large asteroids (planetesimals) were constantly hitting the Moon and the other planets.

“A shard* from such a collision could have reached the orbit of Mars when the planet was still forming and was trapped in its Trojan clouds.”

There are said to be other explanations for the similarities though, and the asteroid could even be a fragment of Mars itself.

More research is needed before we can be certain either way.

These findings have been reported online in the journal Icarus.

Earth and moon. media_cameraThe Moon is a natural satellite that orbits Earth.


  • The Moon is a natural satellite that orbits our planet
  • It is Earth’s only natural satellite and is the fifth biggest in the Solar System
  • The Moon measures almost 3473km across, roughly 0.27 times the diameter of Earth
  • Temperatures on the Moon range from -173C to 260C
  • Experts assumed the Moon was another planet, until mathematician and astronomer Nicolaus Copernicus outlined his theory about our Solar System in 1543
  • It was eventually assigned to a “class” after astronomer Galileo Galilei discovered four moons orbiting Jupiter in 1610
  • The Moon is believed to have formed about 4.51 billion years ago
  • The strength of its gravitational field is about a sixth of Earth’s gravity
  • Earth and the Moon have “synchronous rotation”, which means we always see the same side of the Moon – hence the phrase “dark side of the Moon”
  • The Moon’s surface is actually dark, but appears bright in the sky due to its reflective ground
  • During a solar eclipse, the Moon covers the Sun almost completely. Both objects appear a similar size in the sky because the Sun is both 400 times larger and farther away
  • The first spacecraft to reach the Moon was in 1959, as part of the Soviet Union’s Lunar program
  • The first manned orbital mission was Nasa’s Apollo 8 in 1968
  • And the first manned lunar landing was in 1969, as part of the Apollo 11 mission
FILE - This July 20, 1969 file photo released by NASA shows astronaut Edwin E. "Buzz" Aldrin Jr. posing for a photograph beside the U.S. flag deployed on the moon during the Apollo 11 mission. The family of Neil Armstrong, the first man to walk on the moon, says he has died at age 82. A statement from the family says he died following complications resulting from cardiovascular procedures. It doesn't say where he died. Armstrong commanded the Apollo 11 spacecraft that landed on the moon July 20, 1969. He radioed back to Earth the historic news of "one giant leap for mankind." Armstrong and fellow astronaut Edwin "Buzz" Aldrin spent nearly three hours walking on the moon, collecting samples, conducting experiments and taking photographs. In all, 12 Americans walked on the moon from 1969 to 1972. (AP Photo/NASA, Neil A. Armstrong, file) media_cameraAstronaut Buzz Aldrin poses for a photograph next to the US flag after landing on the Moon in the 1969 Apollo 11 mission. Picture: AP Photo/NASA

This story was first published on The Sun and is republished with permission.

NASA's Asteroid Defence System


  • composition: what it is made up of
  • relic: object from an earlier time
  • spectrum: range
  • dead-ringer: the same
  • celestial: belonging to outer space
  • debris: broken pieces
  • shard: piece


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  1. What is the name of the tool scientists used to observe the asteroid?
  2. Which planet’s orbit does the asteroid share?
  3. Where is the Armagh Observatory and Planetarium?
  4. Most of the Trojan asteroids we know about share the orbit of which other planet?
  5. What is the temperature range on the Moon?


1. Uncertain language
This news story reports on things that researchers think may be true but are not certain about. The language they have used when talking about their hypotheses reflects this. Read the story carefully and jot down all of the words or phrases you can find that show that the information is unproven.

Then, think of five different words or phrases that could also be used to show that an idea is uncertain.

Time: allow 20 minutes to complete this activity
Curriculum Links: English

2. Extension
Arrange the following words or phrases along a scale that shows the level of certainty you think is indicated by the use of the word. Words that indicate a high level of certainty are known as “high modality” words and are useful in persuasive writing.

  • definitely
  • possibly
  • it is thought that
  • undoubtedly
  • maybe
  • perhaps
  • absolutely
  • could be
  • I believe that
  • potentially
  • surely
  • unquestionably

Time: allow 10 minutes to complete this activity 
Curriculum Links: English

Down-Level It
When you up-level a sentence, you do things to it to improve it: make it more interesting, or more complex.

But sometimes, when we read something it can be too complex and we don’t understand it very well. You ask someone to explain it to you, they do (in a simpler way) and you think, well why didn’t they just say that?

Go through the article and find a sentence or two that is complex, or hard to read.

Ask an adult what it means, or try and look some of the words up in the glossary.

Once you know what it means, see if you can rewrite it in a simpler way – down-level it.

Make sure you don’t change the meaning of the sentence in any way though.

HAVE YOUR SAY: What would you like to use the Very Large Telescope to observe in space?
No one-word answers. Use full sentences to explain your thinking. No comments will be published until approved by editors.

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