A study has detailed why there are at least three asteroids which pose a potential threat to Earth and why current observation stations aren't adequate in stopping them.
A study - titled The Invisible Threat: Assessing the Collisional Hazard Posed by the Undiscovered Venus Co-Orbital Asteroids - has revealed there are a bunch of co-orbital asteroids of Venus which could pose a threat to Earth.
The research - co-authored by Valerio Carruba and colleagues at São Paulo University - explains there are '20 co-orbital asteroids of Venus' which are 'currently known' about but while their 'co-orbital status protects' them from 'close approaches to Venus,' the same can't be said when it comes to them 'encountering Earth'.
So, in order to figure out just how many pose a risk and to what extent, the study investigated how detectable the asteroids really are both from Earth and space observatories and how predictable they subsequently are.
The study's assessment of the possible threat of Venus co-orbitals to Earth
The study revealed there are currently only 'twenty co-orbital asteroids of Venus' which are 'currently known' about but many others remain unable to be seen with the current gear being used to monitor space.
Many near-Earth asteroids (NEAs) have been tracked for decades however, co-orbital asteroids of Venus are harder to locate and that can make them more unpredictable.
But what makes an asteroid potentially hazardous to Earth? Well, 'a Potentially Hazardous Asteroid (PHA) must have a minimum diameter of about 140 meters and come within 0.05 astronomical units (au) of Earth’s orbit,' the study explains.
The study used analytical models and simulations to identify how many of Venus' co-orbital asteroids may pose a threat to Earth and subsequently be considered PHAs and assess how easily they'll be able to be detected from Earth.
But what did it find?
Why at least three of Venus' co-orbital asteroids pose a threat to Earth
The study 'identified six co-orbital asteroids that can become PHAs in the next ≃12000 years' and there is 'a range of orbits with e<0.38, larger at lower inclinations, for which Venus’ co-orbitals can pose a collisional hazard to Earth'.
And three asteroids in particular - '2020 SB, 524522, and 2020 CL1' - were identified as posing the greatest current threat to Earth.
They were identified as having a Minimum Orbital Intersection Distance (MOID) - which is the distance between the closest points of two objects’ orbits - with Earth of less than 0.0005 au'.
The asteroids are predicted as having diameters of 330, 300 and 390 meters.
'Assuming a density of 1,200 kg/m3' alongside the 'impact angle,' the study predicts - should the asteroids hit Earth - they would do so at a velocity of 11.2 km/s.
The study continued: "And impacts on sedimentary rocks, these objects could form craters with diameters from 2.2 to 3.4 Km, and release energies at impact from 1.5 to 4.1×102 Megatons TNT, which is more than enough to destroy large cities.
"This corresponds to a level eight in the Torino scale, i.e., a collision capable of causing localized destruction for an impact over land or possibly a tsunami if close offshore."
Suggestions for future to better protect Earth from Venus' co-orbital asteroids
The study explains 'a single telescope mission' still may not help much as 'sky coverage may be limited' and 'NEAs and PHAs may be observable for limited times and geometries, so limiting the accuracy of the possible retrieved orbit'.
The study states: "The recent discovery of the PHA 2024 YR4, an asteroid that reached the highest ever impact probability for an asteroid larger than 20 meters and is a potential “city-killer” showed that there are still undetected asteroids in the inner Solar System with the potential to cause significant damage to Earth.
"Among these, low-e Venus’ co-orbitals pose a unique challenge, because of the difficulties in detecting and following such objects from Earth.
"While surveys like those from the Rubin Observatory may be able to detect some of these asteroids in the near future, we believe that only a dedicated observational campaign from a space-based missions near Venus [...] could potentially map and discover all the still 'invisible' PHA among Venus’ co-orbital asteroids."
The study suggests a 'Venus-based observer' would better help protect Earth from any such asteroids in how it would help provide 'consistent opportunities for detecting and tracking co-orbital objects'.
"Though still subject to fundamental visibility constraints due to solar elongation limits," it added.