The European Space Agency (ESA) is Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
Find out more about space activities in our 23 Member States, and understand how ESA works together with their national agencies, institutions and organisations.
Exploring our Solar System and unlocking the secrets of the Universe
Go to topicProtecting life and infrastructure on Earth and in orbit
Go to topicUsing space to benefit citizens and meet future challenges on Earth
Go to topicMaking space accessible and developing the technologies for the future
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ESA is unique in that it has two missions at Venus and Mars operating simultaneously. Both missions are carrying identical instruments, ASPERA-3
and ASPERA-4, to study the interactions of solar wind with the planets. In addition, Mars Express and Venus Express are the only missions capable
of such measurements at present.
Mars and Venus have similar interactions with the solar wind and similar carbon dioxide atmospheres. Thanks to ASPERA measurements, it was also
possible to discover striking differences.
The plasma (a gas of charged particles) escaping the two planets has very different compositions. At Venus, it is composed of ionised oxygen (O+),
ionised helium (He+) and ionised hydrogen (H+); at Mars the escaping plasma is composed of ionised molecular and atomic oxygen (O2
+, O+) and
ionised carbon dioxide (CO2
+).
The relative size of the interaction region is much larger at Mars than at Venus. The differences are due to different sizes (and thus mass and gravity)
of the planets.