Understanding Asteroid Bennu's Close Passes and Its Potential Impact on Earth

Asteroid Bennu is a near-Earth object (NEO) that passes close to our planet roughly every six years. Since its discovery, scientists have been closely monitoring its orbit, trajectory, and potential hazards. In this article, we will explore the concept of a 'close pass,' the distance threshold, and the impact it could have on Earth.

What Defines a 'Close Pass'?

There is no universally agreed-upon definition for a 'close pass' of an asteroid. However, one common reference point is when the asteroid travels within a certain distance from Earth's orbit. For example, a 'close pass' is often defined as being within 0.05 AU (Astronomical Units), which is approximately 7.5 million kilometers or 19.5 times the distance to the Moon.

Determining the Degree of Closeness

Various factors contribute to defining a 'close pass.' These include the distance from Earth, the relative velocity, and the size and composition of the asteroid. For NEAs, a distance less than 0.01 AU, roughly 930,000 miles, is generally considered a close encounter. This is the case for expected close approaches of Bennu.

Comparing Distances

To give context, since 27 million kilometers has been termed a 'close pass' before, we can break it down by dividing by the Moon's average orbital distance of 400,000 kilometers. This gives us a seemingly maximum figure of 67.5 lunar orbit radii. However, a more precise definition for a 'close pass' is within 0.05 AU, which is about 7.5 million kilometers or 19.5 times the distance to the Moon.

Bennu's Specifics

Bennu is the asteroid with the highest risk rating due to its close approach frequency and size. It has a diameter of 490 meters (1,610 feet) and a mass of 78 billion kg. Its orbit crosses Earth's path and it is therefore a significant concern for potential impacts.

Future Close Approaches

Below are some of Bennu's future close approaches:

Year Closest Approach (AU) Distance to Moon (km) 2022 0.035 3412367 2035 0.00197 183372 2135 0.001816954 160729 2182 0.000244 23471

Note that it does not actually make a close approach every six years. Its orbital period is 437 days, so it is not in sync with Earth's orbit. However, its orbit does cross ours, making it a recurring concern.

Impact Risk and Mitigation

If Bennu were to impact Earth, the potential consequences would be devastating. The impact would be estimated at around 1200 megatons, which is equivalent to the force of over 10,000 atomic bombs detonating at once. This could cause widespread devastation, including massive tsunamis in water impacts or the destruction of entire regions in land impacts.

Precautionary Measures

Thankfully, NASA and other space agencies have the technology and capabilities to address the potential threats posed by Bennu. If it were on a direct route to Earth, they would be certain to change its orbit if required. Techniques such as nuclear explosives could be used to alter the asteroid's trajectory, ensuring a safer path for Earth.

Monitoring and Research

Scientists are constantly monitoring Bennu's trajectory, using data from various space missions and observations. Their research helps to refine our understanding of the asteroid's behavior and potential risks. This includes the use of radar and telescopic observations to gather detailed information about the asteroid's size, shape, and orbit.

Conclusion

In conclusion, while the upcoming close pass of Bennu is a cause for cautious monitoring, the scientific community is well-equipped to handle the potential challenges. Understanding the definitions and thresholds for 'close passes' and the specific characteristics of NEAs like Bennu is crucial for ensuring the safety of our planet.

Asteroid Bennu Close Pass

By combining data and scientific research, we can effectively manage the risks posed by near-Earth asteroids like Bennu.