Your letters and comments on the January 20, 2018 issue of Science News
The possibility that human visitors could carry Earth-based microbes to the Red Planet has roiled the Mars research community, Lisa Grossman reported in “How to keep humans from ruining the search for life on Mars” (SN: 1/20/18, p. 22).
Reader Bruce Merchant speculated that Mars would need a protective global magnetic field to sustain a life-friendly environment. But the planet’s core cannot generate such a field, he wrote. Merchant suggested that the presence or absence of magnetic fields might be one way to tell whether a planet could support life. “Can we determine that for exoplanets?” he asked.
It’s unclear if a planet