The Bridge V Learning Edition 1 ; our solar system | Page 5

Rocky Planets
T he f ou r ro ck y pl an e ts (Mercu ry, Ve nu s , Ea rth a nd Ma rs ) a re very d e ns e a nd
c ompa ra ti vel y smal l . T hei r a tmos phe res a re ve ry th in o r no n -ex is ten t, wi th the
e xc ep tion of th a t of Ve nu s .
Mercury
Me rc u ry is the p la ne t n ea res t to th e Su n . It h as no a tmos ph e re a nd i ts su rfa ce ,
i s c o vered wi th cra te rs . Me rc ury o rbi ts the S un o nc e in ju s t 8 8 da ys an d h as no
moo ns . Th ere a re s eve re tempe ra tu re diffe ren ce s on i ts su rf ace : 38 0 ° C on the
s id e fa cin g th e Su n , a nd -180 ° C on the nig h t s ide! Thi s i s b ec au se da y a nd
n igh t sh if t ve ry slo wly o n Mercu ry, b ec au se of i ts s lo w s pi n . Also , the re i s no
a tm osp he re to trap the he a t a t nig h t.