F(p)=mg/3=F(e)/3 F(p)==2GM(p)m/r(e)^2 F(e)=6GM(p)m/r(e)^2 6GM(p)m/r(e)^2=GM(e)m/r(e)^2 M(p)=M(e)/6 Индекс "е" значит earth, "p" - another planet