Some­thing inter­est­ing occurred in the late 1960’s as part of the Apol­lo pro­gram.  The uncrewed probe Sur­vey­or 3 was land­ed in the Ocean of storms in 1967. Part of the Apol­lo 12 mis­sion, the sec­ond crewed land­ing in 1969, was to retrieve engi­neer­ing sam­ples from Sur­vey­or 3. That mis­sion was a suc­cess, but that is only the begin­ning of the story.

For two years, Sur­vey­or had unin­tend­ed pas­sen­gers wait­ing on the sur­face of the Moon for 31 months. They were bac­te­ria spores that man­aged to sur­vive in the vac­u­um of space.  The very fact of their sur­vival begs the ques­tion: Are their nat­ur­al process­es that can move life from one plan­et to anoth­er over inter­plan­e­tary dis­tances? And if that is pos­si­ble: Is it pos­si­ble for those same process­es to move life inter­stel­lar distances?

Recent­ly, an addi­tion­al piece to the pansper­mia sto­ry was added.  An object passed through the solar sys­tem. The tra­jec­to­ry of the object con­firmed that it was inter­stel­lar in ori­gin.  It is called Oumua­mua. Mod­els have sug­gest­ed that there might be 10 mil­lion such objects near­by the sun (see Our Solar Sys­tem… from inverse).  With that many objects we like­ly have sam­ples from 10 mil­lion stars from around the Milky Way. Sim­i­lar­ly, we could have sent sam­ples to around the same num­ber of stars.

Tak­ing a page from the Drake Equa­tion, we can look at a prob­a­bil­i­ty of obtain­ing a sam­ple of life from anoth­er life bear­ing plan­et.  Num­ber of objects \inline N_o, times the prob­a­bil­i­ty of plan­ets per sys­tem \inline f_p, times the num­ber of plan­ets per sys­tem \inline n_p, times the prob­a­bil­i­ty of a plan­et hav­ing life \inline f_l, times the prob­a­bil­i­ty the sam­ple sur­vived the jour­ney \inline f_s should give us the num­ber of live sam­ples that could be with­in reach: \inline N_s=N_o f_p n_p f_l f_s.