Robert Silverberg 
Lost Race of Mars 

Are the Old Martians really a lost race – just withered mummies lying in dark caves? Or are they still alive – somewhere on the red planet?Sally and Jim must find out. They must help their father discover if the Old Martians exist. His life work as a scientist is at stake!But it’s not easy. They are only visitors to the Mars colony in this year 2017. And no one really wants them there.