For many people, the single greatest human achievement of the 20th century happened on July 20th, 1969 when Neil Armstrong and Buzz Aldrin walked on the moon, and a large proportion of those people probably hope for a similar spectacle on Mars in the coming decades.
But aside from it being cool, is there actually any reason to send humans to these far-flung places?
Britain's Astronomer Royal, Martin Rees, and Astrophysicist & Science Writer Donald Goldsmith consider this very question in their new book 'The End of Astronauts: Why Robots are the Future of Exploration'.
They joined Jonathan to discuss.
Also joining Jonathan to run through the week's top science stories are Dr. Lara Dungan and Dr. Jessamyn Fairfield.