Magnetic Asteroids: Shielding Required?
When we think of Asteroid defense, most people of the latter generations probably think of Bruce Willis drilling a hole deep into an asteroid and planting a nuke to blow it to smithereens before it risks impacting the Earth to prevent Armageddon ... but we don't seem to have come to realize another potential associated risk that has indeed, captured my eye..
Our planet itself is a giant magnetic bubble, and seemingly, some asteroids ALSO have a certain level of magnetism based on their composition. The more iron and nickle, the more of a tug these asteroids may possess. Now, while it may not be enough to tug on Earth physically... like the Moon, they could likely affect liquid or plasma matter on or within the Earth, such as oceans, or the composition and structure of metallic elements within the mantle.
We don't fully know the composition of all asteroids that fly by, but I would imagine a very highly charged magnet, flying by the Earth, could very well have an impact on our magnetic field and everything connected to it. These Asteroids may still have unseen effects on us, even when they don't necessarily impact. A good example? Just last week, on Friday December the 13th an asteroid (2019 XO1) passed by the Earth that was an Aten-class asteroid. Aten asteroids are a group of asteroids whose orbits bring them into very close proximity with Earth. By definition, Atens are Earth-crossing asteroids (with a distance of a < 1.0 AU and Q > 0.983 AU) and some of them may very well have magnetic elements within their composition. Yellowstone - 3.5 Earthquake (Sunday December 15)