• Recently, a leftover piece of a spacecraft flying (of Chang’e 5-T1 – a lunar mission of China) through space reportedly hit the surface of the moon creating a new crater that may be around 65 feet wide.
  • This is the first recorded unintentional case of space junk hitting the moon.
  • The speed, trajectory, and time of impact were calculated using earth-based telescope observations called Project Pluto.
  • Project Pluto is a blog that tracks near-earth objects, which was created by American astronomer Bill Gray. He is also the creator of a popular astronomy software called Guide.

Space Junk

  • Space debris, also called space junk, artificial material that is orbiting Earth but is no longer functional.
  • This material can be as large as a discarded rocket stage or as small as a microscopic chip of paint.
  • Much of the debris is in low Earth orbit, within 2,000 km of Earth’s surface, though some debris can be found in geostationary orbit 35,786 km above the Equator.
  • The free floating space debris is a potential hazard for operational satellites and colliding with them can leave the satellites dysfunctional.
  • This is referred to as Kessler Syndrome, named after NASA scientist Donald Kessler in 1978.
  • It says if there is too much space junk in orbit, it could result in a chain reaction where more and more objects will collide and create new space junk in the process, to the point where Earth’s orbit becomes unusable – a Domino Effect.
  • With countries launching more and more satellites, each one of them being a strategic or commercial asset, avoiding collisions could become a challenge in the future.
  • Clearspace-1 (of European Space Agency), which is scheduled to launch in 2025, will be the first space mission to eliminate debris from orbit.

Lunar Craters

  • Lunar Craters are bowl-shaped landforms created by Volcanism and Cratering, about 4.5 billion years ago, shortly after Earth was formed.
  • There are hundreds of thousands of moon craters ranging from less than a mile across to giant basins.
  • The largest crater on the Moon is called South Pole-Aitken Basin.
  • Further, throughout its existence, the Moon has been bombarded by comets and asteroid chunks, and those created the many impact craters we see today.
  • Moon’s lack of water, atmosphere, and tectonic plates, there is little erosion, and craters are found that exceed two billion years in age.
  • Mitra Crater on Moon is named after Indian radio physicist Sisir Kumar Mitra.

Difference between Craters on the Moon and Earth

  • Both the earth and the moon have been hit by multiple objects like asteroids throughout their existence, but craters on the moon are of a more permanent nature than those on earth.
  • This is because of processes like erosion, tectonics, and volcanism.
  • According to NASA, these three processes keep the surface of the earth crater-free and remove traces of collisions that have happened in the past.
  • Currently, the earth has less than 200 known craters while the moon has thousands.
  • An absence of atmosphere means there is no wind system and no weather on the moon, and hence no cause for erosion of existing craters.
  • The absence of tectonics prevents the moon’s surface from forming new rocks or causing a shift in the existing surface patterns, unlike that on earth.
  • Lastly, the absence of volcanism (in recent history) makes it impossible for craters to be covered.


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