Earths Second Moon
We all know that the Earth has a Moon which on most nights we can look up into the sky and see it in its different phases. Occasionally the Earth has more than one moon. Asteroids can come close to the Earth and become captured by the Earths gravity and trapped for a time to become an Earth satellite or moon. These mini moons usually don`t last long orbiting the Earth when they are flung off to continue their travel through the solar system again.
Now an asteroid is likely to become a new mini moon and it is called 2020 SO which arrived in October 2020 and is expected to be ejected out of the Earths orbit in May 2021. Previously two prior mini moons were confirmed, they were RH 120 which orbited the Earth from September 2006 until June 2007. While the second was 2020 CD3 which was captured in 2015 or 16 and was believed to have been liberated in May 2020.
What was different about 2020 SO was that it had a relatively low velocity compared to a typical asteroid. An asteroid would typically have an average rate of travel of 58,000 feet (18 km) per second. 2020 SO also has an orbital patch which is similar to the Earths which is roughly similar to one Earth years.
If it is not an asteroid what could it be?. From observations already made by NASA, the object has the dimensions which are very similar to the discarded centaur rocket stage which launch the Surveyor 2 spacecraft to the Moon and landed on the lunar surface in September 1966. The centaur rocket stage was jettisoned when the Surveyor was on its way to the Moon. The Centaur rocket stage continued onwards with its journey past the Moon to orbit the Sun. Now it has returned to be captured briefly by the Earth.
It will not be near enough to enter the Earths atmosphere but it is still hoped that images could be taken. After some 54 years in space it is hoped that some observational science could be made. It would be interesting to see what it looks like now and how the time in space has affected it surface. Using spectroscopy it is hoped that this could be found out as to how its painted surface would look like and also what is the state of the surface with impacts of dust and micrometeorites have had on the skin. It was confirmed to be the Centaur stage from detailed observations of the spectral data from the object. It showed that it was made from stainless steel which was used in the centaur stages construction. The spectral data was compared with the spectral data obtained from a known similar rocket stage travelling through space.
An image from the Virtual Telescope Project showed that it left a dotted trail pattern which suggested that it was rotating every 10 seconds which gave the difference in its brightness.
Surveyor 2 launch
Atlas centaur rocket Mariner 9 launch stamp
Surveyor 7 stamp
Image of 2020 SO
Surveyor 2 Centaur rocket stage