The Latin prefix “apt-” means “fit” or “adapt”, explaining the function of this rover wheel: the Aptowheel. When the rover’s cameras detect an upcoming obstacle or sand trap, an electromagnet fixed to a rotating shaft activates, triggering a mechanism that draws a liquid (held within the wheel’s white piping) inwards and causes the Aptowheel’s eight pistons to contract. This liquid has been designated as methylcyclopentane (C6H12) for its low freezing point and high flash point, preventing both freezing and combustion when on Mars. Each of the pistons is structurally affixed to a rigid central frame made of an alpha-titanium alloy (both sturdy and lightweight) and four curved sturdy outer sheets of metal ion-infused graphene rubber. These outer sheets -- covered in regularly-spaced shallow ridges and tall grousers -- are therefore able to change the effective shape of the wheel in order to suit the terrain by either contracting or expanding.