In a call with the International Space Station today, President Trump said that he'd like to get astronauts to Mars "at worst, during [his] second term."
Public: The Orion program, the Space Shuttle's successor designed to take humanity out of low-Earth orbit, doesn't have a crewed mission scheduled until 2021, and it's likely to be delayed until at least 2023. NASA won't commit to a firm estimate for a planned Mars mission, saying it hopes it'll launch in the 2030s.
Private: SpaceX's Interplanetary Transport System had been scheduled to launch its first crewed mission in 2024, but that was contingent on a schedule with a first launch to Mars in 2018 — with a spacecraft that isn't scheduled to have its first orbital test until later this year.
Why it matters:
Trump's proposed NASA budget kept Mars funding intact, and political willpower goes a long way in shrinking the notoriously long timescales for spaceflight.