Well going into space has clear advantages for our species. Firstly, it provides a backup in case something happens to earth, like if it gets hit by an asteroid. It could also potentially be untouched by a nasty war on earth, but odds are it would get dragged into it. Secondly there are commercial possibilities like mining in space, or space real estate . Thirdly, astronomy is one of two ways we expand our knowledge of physics (the other being particle accelerators), and new physics can lead to good things down the line.

There are benefits of exploring the oceans too, like maybe finding some missing link species and learning about biology maybe some geology. But they seem much lesser to me.