Mars is not and at no point in the next century (likely centuries) capable of being a backup of anything for Earth. It has zero industry, difficult to exploit natural resources, and the surface and subsurface environments are completely hostile to human life. A human can only live there with significant amounts of advanced technology supporting them.
A tape drive can be a back up for a hard drive because it is only mechanically different from a hard drive. A tape drive can use the same data bus, uses the same electricity, and stores the same data as a hard drive. It's just slower and less convenient. Mars is to Earth what soap bubbles for data storage are to a hard drive. They might be able to store data but they're fantastically fragile and trying to implement the system would be a waste of time.
I had already +1'd you here but literally lol'd here.
Seriously though, I have no idea why you are being downvoted; this is a pretty insightful comment. I guess your first sentence hit too close to home.