JOHNSTOWN, PA - JULY 30: Steel workers look on during a campaign rally with democratic presidential nominee former Secretary of State Hillary Clinton and democratic vice presidential nominee U.S. Sen Tim Kaine (D-VA) at Johnstown Wire Technologies on July 30, 2016 in Johnstown, Pennsylvania. Hillary Clinton and Tim Kaine are continuing their a three-day bus tour through Pennsylvania and Ohio. (Photo by Justin Sullivan/Getty Images)

BEVERLY HILLS, CA - JULY 30: (L-R Back Row) NASA's Jennifer Trosper, actors Anamaria Marinca, Sammi Rotibi, Clementine Poidatz, Ben Cotton and Professor of Space Technology at Georgia Institute of Technology and MARS Consulting Scientist Dr. Robert Braun (L-R Front Row) author Stephen Petranek, executive producer Justin Wilkes, actors Jihae, Olivier Martinez, director Everardo Gout and author Andy Weir speak onstage during the 'National Geographic Channel - MARS' panel discussion at the National Geographic Channels portion of the 2016 Television Critics Association Summer Tour at The Beverly Hilton Hotel on July 30, 2016 in Beverly Hills, California. (Photo by Frederick M. Brown/Getty Images)

BEVERLY HILLS, CA - JULY 30: (L-R Back Row) NASA's Jennifer Trosper, actors Anamaria Marinca, Sammi Rotibi, Clementine Poidatz, Ben Cotton and Professor of Space Technology at Georgia Institute of Technology and MARS Consulting Scientist Dr. Robert Braun (L-R Front Row) author Stephen Petranek, executive producer Justin Wilkes, actors Jihae, Olivier Martinez, director Everardo Gout and author Andy Weir speak onstage during the 'National Geographic Channel - MARS' panel discussion at the National Geographic Channels portion of the 2016 Television Critics Association Summer Tour at The Beverly Hilton Hotel on July 30, 2016 in Beverly Hills, California. (Photo by Frederick M. Brown/Getty Images)

BEVERLY HILLS, CA - JULY 30: (L-R Back Row) NASA's Jennifer Trosper, actors Anamaria Marinca, Sammi Rotibi, Clementine Poidatz, Ben Cotton and Professor of Space Technology at Georgia Institute of Technology and MARS Consulting Scientist Dr. Robert Braun (L-R Front Row) author Stephen Petranek, executive producer Justin Wilkes, actors Jihae, Olivier Martinez, director Everardo Gout and author Andy Weir speak onstage during the 'National Geographic Channel - MARS' panel discussion at the National Geographic Channels portion of the 2016 Television Critics Association Summer Tour at The Beverly Hilton Hotel on July 30, 2016 in Beverly Hills, California. (Photo by Frederick M. Brown/Getty Images)

Democratic presidential candidate Hillary Clinton speaks at Johnstown Wire Technologies in Johnstown, Pennsylvania, July 30, 2016. REUTERS/Aaron P. Bernstein

Democratic presidential candidate Hillary Clinton and vice presidential candidate Senator Tim Kaine (D-VA) tour Johnstown Wire Technologies along with CEO Ron Shaffer and former U.S. president Bill Clinton in Johnstown, Pennsylvania, July 30, 2016. REUTERS/Aaron P. Bernstein

Democratic presidential candidate Hillary Clinton and vice presidential candidate Senator Tim Kaine (D-VA) greet supporters at Johnstown Wire Technologies in Johnstown, Pennsylvania, July 30, 2016. REUTERS/Aaron P. Bernstein

Supporters of Republican presidential candidate Donald Trump protest as Democratic presidential candidate Hillary Clinton and vice presidential candidate Senator Tim Kaine (D-VA) arrive at Johnstown Wire Technologies in Johnstown, Pennsylvania, U.S., July 30, 2016. REUTERS/Aaron P. Bernstein