I was thinking on this the other day. Sir Hubert Wilkins was the first to try to reach the North Pole by submarine, in his submarine Nautilus, in 1931. The expedition did fail, but they lived to see another day.
On May 17, 1959, the USS Skate did do so. She deposited Wilkins's ashes in a ceremony there.
Wouldn't it be something if Hawking's ashes were deposited on Mars in the first manned trip there. It seems more fitting than say sending them off into deep space. That way he could be visited by future generations.