Why has the mother been compared to the “late winter’s moon”?

The poet offers her readers to perceive her contempt towards old age through another image of the mother as the “late winter’s moon”. Just as the moon appears vague, misty, obscure and dull in winters, the mother seems to be nearing towards her death with a pale and uncolored face which seems to be bereft of life, thus resembling a corpse. She appears devoid of shine and strength which the poet associates only with adulthood. She wants to escape the untamed passage of time and the nearing of death.