<a href="https:&#x2F;&#x2F;twitter.com&#x2F;neiltyson&#x2F;status&#x2F;730719094111109121" rel="nofollow">https:&#x2F;&#x2F;twitter.com&#x2F;neiltyson&#x2F;status&#x2F;730719094111109121</a><p>&gt; More than half of its volume is ice.  So nobody should be surprised it shares properties with comets.