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I'm surprised that only the Viking lander bothered to test for signs of life - especially since the results were "confusing".

Guvante 3y ago
IIRC we have been avoiding going anywhere where life could be to avoid contamination. Making a lander where we know there are no earth microbes on it is quite difficult and certainly important for testing for life.
- qup 3y ago
  Which places did we avoid going?
  - tcoff91 3y ago
    probably europa and enceladus
    - ralferoo 3y ago
      All these worlds are yours. Except Europa. Attempt no landing there.
  - zokier 3y ago
    For example from the Mars 2020 mission (Perseverance rover) landing site selection: https://marsnext.jpl.nasa.gov/scieng_plantary.cfm https://marsnext.jpl.nasa.gov/scieng_plantary.cfm > A Special Region is defined as a location where the temperature could exceed -28° Celsius (-18.4° Fahrenheit) and water activity is at least 0.5. Water is key to life as we know it, and water activity considers the availability of water and water vapor as a potential support for life processes. > The Mars 2020 mission is restricted from landing in, entering, or creating, a Special Region on Mars [...] > Thus, the Mars 2020 mission is also restricted from landing in sites where scientists suspect water, brine, or water ice could be present, or could be induced, within 5 meters (about 16.4 feet) of the surface
- asdff 3y ago
  It takes them seven months to fly a rover to mars. They could potentially devise a way to expose the rover to space during these months to sterilize it.
  - tastyfreeze 3y ago
    Rovers are assembled in a clean room and space doesn't sterilize all life. It is impossible to know with certainty that a rover is sterile. Even autoclaving the whole rover doesn't guarantee sterility. https://www.sciencealert.com/a-bunch-of-earth-organisms-were-stuck-outside-the-iss-and-survived https://www.sciencealert.com/a-bunch-of-earth-organisms-were...
    - asdff 3y ago
      There has to be some limit on radiation resistance for these microorganisms. At the end of the day, DNA is a fragile molecule and it can be degraded. Maybe the rover could be overbombarded with radiation on this journey, if the background radiation in space is insufficient.
      - tastyfreeze 3y ago
        We have found life in every environment we have explored on Earth. That includes surviving high radiation environments. https://en.wikipedia.org/wiki/Deinococcus_radiodurans https://en.wikipedia.org/wiki/Deinococcus_radiodurans
        asdff 3y ago
        Radiodurans probably still has some limit where the rate of radiation is higher than its ability to repair fragmented DNA, at which point things snowball and the DNA is quickly broken down to its constituent bases and there would be no template at all in which to initiate any repair.
sbierwagen 3y ago
They haven't bothered with labeled release or adding water to soil. Curiosity does have a similar oven+GCMS setup to Viking, which has indeed found funny organic chemicals in some soil samples: https://en.wikipedia.org/wiki/Sample_Analysis_at_Mars https://en.wikipedia.org/wiki/Sample_Analysis_at_Mars

Guvante 3y ago

IIRC we have been avoiding going anywhere where life could be to avoid contamination. Making a lander where we know there are no earth microbes on it is quite difficult and certainly important for testing for life.

qup 3y ago
Which places did we avoid going?
- tcoff91 3y ago
  probably europa and enceladus
  - ralferoo 3y ago
    All these worlds are yours. Except Europa. Attempt no landing there.
- zokier 3y ago
  For example from the Mars 2020 mission (Perseverance rover) landing site selection: https://marsnext.jpl.nasa.gov/scieng_plantary.cfm https://marsnext.jpl.nasa.gov/scieng_plantary.cfm > A Special Region is defined as a location where the temperature could exceed -28° Celsius (-18.4° Fahrenheit) and water activity is at least 0.5. Water is key to life as we know it, and water activity considers the availability of water and water vapor as a potential support for life processes. > The Mars 2020 mission is restricted from landing in, entering, or creating, a Special Region on Mars [...] > Thus, the Mars 2020 mission is also restricted from landing in sites where scientists suspect water, brine, or water ice could be present, or could be induced, within 5 meters (about 16.4 feet) of the surface
asdff 3y ago
It takes them seven months to fly a rover to mars. They could potentially devise a way to expose the rover to space during these months to sterilize it.
- tastyfreeze 3y ago
  Rovers are assembled in a clean room and space doesn't sterilize all life. It is impossible to know with certainty that a rover is sterile. Even autoclaving the whole rover doesn't guarantee sterility. https://www.sciencealert.com/a-bunch-of-earth-organisms-were-stuck-outside-the-iss-and-survived https://www.sciencealert.com/a-bunch-of-earth-organisms-were...
  - asdff 3y ago
    There has to be some limit on radiation resistance for these microorganisms. At the end of the day, DNA is a fragile molecule and it can be degraded. Maybe the rover could be overbombarded with radiation on this journey, if the background radiation in space is insufficient.
    - tastyfreeze 3y ago
      We have found life in every environment we have explored on Earth. That includes surviving high radiation environments. https://en.wikipedia.org/wiki/Deinococcus_radiodurans https://en.wikipedia.org/wiki/Deinococcus_radiodurans
      - asdff 3y ago
        Radiodurans probably still has some limit where the rate of radiation is higher than its ability to repair fragmented DNA, at which point things snowball and the DNA is quickly broken down to its constituent bases and there would be no template at all in which to initiate any repair.

sbierwagen 3y ago

They haven't bothered with labeled release or adding water to soil. Curiosity does have a similar oven+GCMS setup to Viking, which has indeed found funny organic chemicals in some soil samples: https://en.wikipedia.org/wiki/Sample_Analysis_at_Mars https://en.wikipedia.org/wiki/Sample_Analysis_at_Mars