Mercury has a diameter of about 4880 kilometers (3030 miles), and the smallest feature visible in this color image is about 10 kilometers (6 miles) in size.
If the work was published without a notice or if the copyright has expired, it is not in the public domain. Works published between 1964 and 1977 - When published with notice, it has copyright protected for 28 years for first term, with an automatic extension of 67 years for the second term for a total of 95 years.
A book published by a US author in the US, with copyright notice and renewal after 1922 and before 1978 would be copyrighted for 95 years. After that it would most likely be 95 years unless the author was independent (not employed as an author), in which case it would last 70 years after the year of the author's death.