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Loading contentRadio signals travel at the speed of light, but the distances are vast: a message to a crew at Mars can take as much as about twenty minutes each way, so a real-time conversation with Earth is impossible. The delay forces crews to handle emergencies themselves and reshapes how missions far from home are commanded and supported.
Facts on this topic will be cited from these primary and reference sources.
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.