"Repeat after me: Mars matters," NASA Administrator Charles Bolden told the auditorium of participants at the May 5, 2015 Humans to Mars Summit organized by the non-profit Explore Mars, Inc. "Mars matters!" everyone agreed.

But why does Mars matter? "?Because it's there' isn't good enough," stated Bolden. Luckily, summit presenters had a host of compelling reasons for humans to venture to Mars, ranging from political, economic, and at the forefront, scientific reasons.

Bolden explained that Mars' formation and evolution was similar to Earth's, so by studying Mars we can learn more about the Earth and how these two neighboring planets took such different paths. Since Mars once had habitable conditions similar to the Earth, it's possible life arose on both planets. The search for evidence of alien life aims to answer the fundamental science and human question of "Are we alone?"

"We are currently further along than ever before in human history on our Journey to Mars," Bolden announced.

John Grunsfeld, Associate Administrator for NASA's Science Mission Directorate, emphasized that "humans are on Mars today." Our fleet of robotic ambassadors has been collecting Mars science throughout the past four decades. But the value of having humans on the surface making real-time decisions would be priceless.

According to Grunsfeld, Steve Squyres - the Principal Investigator for the Mars Exploration Rovers - once noted that if he were personally on Mars, he could have performed Spirit's and Opportunity's 90-day primary mission in 20 minutes.

Speed is just one advantage humans have in conducting Mars science. During a panel titled "The Extraordinary Science of Mars," planetary scientists from NASA's Goddard Space Flight Center discussed what they'd like to look for on the red planet.

Astrochemist Danny Glavin wants to search for biosignatures in Martian rocks. He would be most excited to see a limited set of amino acids and nucleobases, because biology selects and uses only a few of all the available compounds.

Even more interesting would be if we found a different set of these compounds than life uses on Earth, because that would be evidence that life originated independently on Mars. It would be extremely helpful to have human missions on Mars because people could provide a much greater variety of rock samples than solely robotic missions could provide.

Astrobiologist Jennifer Eigenbrode has reason to believe that Mars is more habitable just under its surface, where material is protected from Mars' extreme radiation and chemical oxidation. She dreams of humans drilling into the rock and collecting and mapping cores. With real-time cognitive responses, astronauts could say, "There, that's the sample we want, that's where we want to look for evidence of life," and be able to immediately fine-tune their observations and get the best possible information.

Pamela Conrad, the Deputy Principal Investigator for the Sample Analysis at Mars instrument suite, has searched high and low on Earth for some place where there is no life - unsuccessfully. Life here is ubiquitous, even in the most extreme environments. She wishes she could do the same search on Mars.

The opportunities for science are limited with robotic rovers, partly because of constraints in communicating with Earth. And, they are too expensive to risk by moving too quickly or by sending them into precarious, though interesting locations. "If I were there," said Conrad, "I would be doing this, this, and this, and this pace [of the robotic rovers] is just way too slow for those of us who are used to working in the field ourselves."

Science is not only the motivation for going to Mars; it is also essential knowledge to have in order for humans to get to Mars. John Grunsfeld explained that before we send humans, it is important to understand Mars' weather and climate cycles, and to know where on Mars there is accessible water to be used for in-situ propellant production. This critical data is coming from current missions like the Mars Science Laboratory and Goddard's MAVEN (Mars Atmosphere and Volatile EvolutioN) orbiter.

Upcoming Mars missions include InSight launching in 2016, the European Space Agency's ExoMars mission launching in 2016 and 2018, and NASA's Mars 2020 rover.

Science is an integral if not driving part of human space exploration. Said Conrad, "Exploration without science is just adventure. There's no return. Exploration is great, but the tools we have at our disposal to bring back societal benefit to all of us, those tools are vested by science."