While the chassis of your car protects most of its delicate bits (and its occupants) from harm, there's very little to stop an object from messing up the underside. This proved an unacceptable situation for the folks over at automotive company Tesla, so they decided the best course of action was to arm the Model S with not one, but three layers of belly protection.
CEO and product architect Elon Musk goes into the details in a blog post on Medium. Essentially, all Model S vehicles produced from 6 March onwards have the new "triple underbody shield" installed and owners who purchased the car before this date can get the upgrade free.
What exactly does the shield consist of? The first line of defence is a "rounded, hollow aluminium bar" that should "deflect objects entirely". Failing that, the bar will absorb most of the impact, making life easier for the other two layers.
Speaking of which, the second protective element is a titanium plate that Musk says has properties "more commonly seen in aerospace or military applications". It's designed to do what titanium does best — remain unyielding in the face of concrete, alternators and whatever else the open road might throw at you.
Finally, a "shallow angle, solid aluminium extrusion" allows the car to "ramp up" over an object if it hasn't been crushed into dust or otherwise pushed out of the way.
The post contains three animated images showing the shields dealing with a variety of objects — the one here shows it smashing a concrete block, Hulk-style. If you'd like to see the GIFs in all their 600 x 375 pixel glory, hit up Musk's post on Medium.