With the increasing interest in human space exploration at the moon and Mars, now is the time to better understand space weather conditions and their effects, in particular during extreme events, beyond the near-Earth environment. While several extreme events have been observed near Earth and along the 1-AU orbit at STEREO-A and -B, there have only been a handful of extreme events observed in orbit and/or at the surface of Mars. Those that have widespread impacts at multiple observer locations (e.g., at Earth, the moon, and Mars) include the 2003 Halloween storm of Solar Cycle 23 and the more recent solar eruptive events on 10 September 2017 of Solar Cycle 24. In this session we will combine the expertise of terrestrial, lunar, and planetary space scientists to stimulate an interdisciplinary discussion about extreme events observed throughout the heliosphere during Solar Cycles 23 and 24. During the session the following questions will be discussed: Under what set of conditions is a space weather event considered an extreme event at a given heliospheric location, for example, at Mars? How does the local space environment at Mars respond to these extreme events (CMEs, SEPs, flares), compared to the 1-AU observers?