Therefore , reaching an orbit around Mercury requires especially expensive rocketry. Mercury 's lack of an atmosphere poses further challenges because it precludes aerobraking .
This is different with superior planets beyond Earth 's orbit where the satellite works against the pull of the Sun .
Reaching an orbit around Mercury requires especially expensive rocketry. Mercury 's lack of an atmosphere poses further challenges because it precludes aerobraking .
This is different with superior planets beyond Earth 's orbit where the satellite works against the pull of the Sun .