Moon is part of Mars

[Fake Messiah]

Why is it hard for robots to look for fossils?

Because for next few decades it will be practically impossible for robots to be trained to look for fossils. I mean even now they send pictures of strange rocks, but without anyone checking it out closely it remains a mystery.
Especially if you're looking for alien organisms. I mean sure they may stumble on something but when it comes to further digging it is almost impossible for now.

For instance in 2013 two Oxford researchers, Carl Benedikt Frey and Michael A. Osborne, published ‘The Future of Employment’, in which they surveyed the likelihood of different professions being taken over by computer algorithms within the next twenty years.
They estimated that 47 % of US jobs are at high risk. For example, there is a 99% probability that by 2033 human telemarketers and insurance underwriters will lose their jobs to algorithms. There is a 98 % probability that the same will happen to sports referees, 97 % that it will happen to cashiers and 96 % to chefs. Waiters – 94 %. Paralegal assistants – 94 %. Tour guides – 91 %. Bakers – 89 %. Bus drivers – 89%. Construction laborers – 88 %. Veterinary assistants – 86 %. Security guards – 84 %. Sailors – 83 %. Bartenders – 77 %. Archivists – 76 %. Carpenters – 72 %. Lifeguards – 67 %. And so on.

BUT the likelihood that computer algorithms will displace archaeologists by 2033 is only 0.7%, because their job requires highly sophisticated types of pattern recognition, and doesn’t produce huge profits. Hence it is improbable that corporations or government will make the necessary investment to automate archaeology within the next twenty years.

https://www.oxfordmartin.ox.ac.uk/downlo...oyment.pdf

Now, when that is being said, there really is no realistic reason to expect that humans will be going to Mars in the next few decades so it will be all left to robots.

Also the chances that some sort of elaborate fossils exist on Mars is probably very low, considering that Mars seemed to be habitable and Earth-like for one or two billions years, which is "short" compared how long it took for life to develop on Earth. But, then again, maybe it went differently there and maybe people are wrong about that assessment.

What is the cost of keeping a crew of humans alive on Mars for 1.5 years, vs the cost of robotic rovers?

Well, you could look at the documentary. It all kind of started back when Bush Sr. in the 80s ordered inspection in how much human mission to Mars would cost. And they got some astronomical numbers like $450 billion because they made it too complicated. But then that guy Zubrin and his team stepped in and they simplified it drastically but then NASA insisted they buff it somewhat more and they got the number of $55 billion over 10 years.
And this Zubrin gives good explanations of why people further still complicate human missions to Mars - because they want their pet projects to be involved. Like many people think that humans need to go on the Moon first, but if you want to go to Mars you just go there. There is no reason to stop on the Moon first, or build spaceship parts there, or train there.

But there are some problems, because radiation on the surface seems to be way too high. And I don't think there are yet rockets that could launch a human crew on Mars and also land it there.

It shouldn't be at all difficult to design a rover that could cover 'hundreds of kilometers'.

Sure. And NASA would send some robots to prepare for humans to land. I mean they could send a balloon to Mars instead of that helicopter.

Robots don't suffer from loneliness or cabin fever.  They don't miss their families and friends.

Sure, but people used to travel to secluded places for many years. Plus there are astronauts that would love to go there and they wouldn't be absent for that long, it would be 3 years.

Of the 50-odd missions to Mars, something more than half have ended in failure.  I'd sooner lose a space probe than a human crew.

Again, there are daring people that would take any risk to go there. For instance, this is what astronaut Mike Mullane wrote about his spaceflights on Space Shuttle to Earth's orbit:

I was as scared as I had ever been in my life. But at that moment, if God had appeared and told me there was a 90 percent probability I wasn’t going to return from this mission alive and had given me an opportunity to jump from that crew van, I would have shouted, “No!” For this rookie flight, I would take a one in ten chance. I had dreamed of this moment since childhood. I had to go. Even if God had given me a vision of what the other nine chances meant, a vision of my charred remains being zipped into one of those body bags, I still would have declined His offer to exit the van. I had to make this flight.