What negative consequence could arise from an alien civilization discovering a Pioneer spacecraft?
We still have much to learn about astrobiology. Myriad steps in the formation of life on Earth remain to be understood. Although the evidence for liquid water once having existed on Mars is overwhelming, we still need to confirm whether life ever existed there. Does life exist in Mars, Europa, Ganymede, or Callisto today? Astronomers are still working to refine their ideas of how organic compounds formed in space. A paramount frontier is detecting life elsewhere in the universe.
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