COLOGNE, GERMANY - MAY 18: Ruth Hemmersbach Head of the Gravitational Biology Section, DLR-CEO Pascale Ehrenfreund, ESA-president Johann-Dietrich Wörner German Chancellor Angela Merkel and the German astronaut Alexander Gerst (L-R) view a moving centrifuge in the DLR-Laboratory for Life Science Experiments during a visit of the European Astronauts Center (EAC) of the European Space Ageny (ESA) on May 18, 2016 in Cologne, Germany. Merkel is visiting the facilities, as well as the nearby German Center for Air and Space Travel (das Deutsche Zentrum fuer Luft- und Raumfahrt, or DLR) in order to promote Germany's participation in ESA's projects, which it sees as important to climate change, energy and agricultural sector research. (Photo by Volker Hartmann/Getty Images)

COLOGNE, GERMANY - MAY 18: Ruth Hemmersbach Head of the Gravitational Biology Section, DLR-CEO Pascale Ehrenfreund, ESA-president Johann-Dietrich Wörner German Chancellor Angela Merkel and the German astronaut Alexander Gerst (L-R) view a moving centrifuge in the DLR-Laboratory for Life Science Experiments during a visit of the European Astronauts Center (EAC) of the European Space Ageny (ESA) on May 18, 2016 in Cologne, Germany. Merkel is visiting the facilities, as well as the nearby German Center for Air and Space Travel (das Deutsche Zentrum fuer Luft- und Raumfahrt, or DLR) in order to promote Germany's participation in ESA's projects, which it sees as important to climate change, energy and agricultural sector research. (Photo by Volker Hartmann/Getty Images)

COLOGNE, GERMANY - MAY 18: Ruth Hemmersbach Head of the Gravitational Biology Section, DLR-CEO Pascale Ehrenfreund, ESA-president Johann-Dietrich Wörner German Chancellor Angela Merkel and the German astronaut Alexander Gerst (L-R) view a moving centrifuge in the DLR-Laboratory for Life Science Experiments during a visit of the European Astronauts Center (EAC) of the European Space Ageny (ESA) on May 18, 2016 in Cologne, Germany. Merkel is visiting the facilities, as well as the nearby German Center for Air and Space Travel (das Deutsche Zentrum fuer Luft- und Raumfahrt, or DLR) in order to promote Germany's participation in ESA's projects, which it sees as important to climate change, energy and agricultural sector research. (Photo by Volker Hartmann/Getty Images)

CAPTION CORRECTION: This is to correct the images #: 532097242,532097230,532097204 by Volker Hartmann, should be astronaut Pascale Ehrenfreund instead of Pascale Ehrenfreundhe. We apologise for any inconvenience. COLOGNE, GERMANY - MAY 18: Ruth Hemmersbach Head of the Gravitational Biology Section, DLR-CEO Pascale Ehrenfreund, ESA-president Johann-Dietrich Wörner German Chancellor Angela Merkel and the German astronaut Alexander Gerst (L-R) view a moving centrifuge in the DLR-Laboratory for Life Science Experiments during a visit of the European Astronauts Center (EAC) of the European Space Ageny (ESA) on May 18, 2016 in Cologne, Germany. Merkel is visiting the facilities, as well as the nearby German Center for Air and Space Travel (das Deutsche Zentrum fuer Luft- und Raumfahrt, or DLR) in order to promote Germany's participation in ESA's projects, which it sees as important to climate change, energy and agricultural sector research. (Photo by Volker Hartmann/Getty Images)

COLOGNE, GERMANY - MAY 18: German Chancellor Angela Merkel meets the german astronaut Alexander Gerst after visiting a centrifuge in the DLR-Laboratory for Life Science Experiments during a visit of the European Astronauts Center (EAC) of the European Space Ageny (ESA) on May 18, 2016 in Cologne, Germany. Merkel is visiting the facilities, as well as the nearby German Center for Air and Space Travel (das Deutsche Zentrum fuer Luft- und Raumfahrt, or DLR) in order to promote Germany's participation in ESA's projects, which it sees is important to climate change, energy and agricultural sector research. (Photo by Volker Hartmann/Getty Images)

COLOGNE, GERMANY - MAY 18: German Chancellor Angela Merkel meets the astronauts Pedro Duque, Samantha Cristoforetti and Jean-Francois Clervoy (L-R) after visiting a centrifuge in the DLR-Laboratory for Life Science Experiments during a visit of the European Astronauts Center (EAC) of the European Space Ageny (ESA) on May 18, 2016 in Cologne, Germany. Merkel is visiting the facilities, as well as the nearby German Center for Air and Space Travel (das Deutsche Zentrum fuer Luft- und Raumfahrt, or DLR) in order to promote Germany's participation in ESA's projects, which it sees is important to climate change, energy and agricultural sector research. (Photo by Volker Hartmann/Getty Images)

Head of the Gravitational Biology Section Ruth Hemmersbach (L-R), DLR-CEO Pascale Ehrenfreundhe, ESA-president Johann-Dietrich Woerner, German Chancellor Angela Merkel and the German astronaut Alexander Gerst view a moving centrifuge in the DLR-Laboratory for Life Science Experiments during visits the European Astronaut Centre (EAC) in Cologne, western Germnay on May 18, 2016. / AFP PHOTO / POOL / SASCHA SCHUERMANNSASCHA SCHUERMANN/AFP/Getty Images

Head of the Gravitational Biology Section Ruth Hemmersbach (L-R), DLR-CEO Pascale Ehrenfreundhe, ESA-president Johann-Dietrich Woerner, German Chancellor Angela Merkel and the German astronaut Alexander Gerst view a moving centrifuge in the DLR-Laboratory for Life Science Experiments during visits the European Astronaut Centre (EAC) in Cologne, western Germnay on May 18, 2016. / AFP PHOTO / POOL / SASCHA SCHUERMANNSASCHA SCHUERMANN/AFP/Getty Images