2011 jeep grand cherokee and 2011 Dodge durango, what is that ball on the bottom grill?

[Motoman88]

Looking at the new jeep and dodge wondering what that ball is on the bottom of the grill and what it does. pictures-- http://gearpatrol.com/blog/2010/09/02/2011-dodge-durango/ http://www.google.com/imgres?imgurl=http://www.roadandtrack.com/var/ezflow_site/storage_RT_NEW/storage/images/highlights/frontpage/additional-coverage/2011-jeep-grand-cherokee/2072257-8-eng-US/2011-jeep-grand-cherokee.jpg&imgrefurl=http://www.roadandtrack.com/tests/impressions/2011-jeep-grand-cherokee&usg=__N7f7lJ9DkHiWzeDwNDBPT1a2qUg=&h=782&w=1280&sz=815&hl=en&start=60&sig2=_589SErnfI2GlcKFpeBK7w&zoom=1&tbnid=bkU-r2JfVwBktM:&tbnh=131&tbnw=165&ei=oh-QTMHuJcifnQep0qm0DA&prev=/images%3Fq%3D2011%2Bjeep%2Bgrand%2Bcherokee%26um%3D1%26hl%3Den%26sa%3DN%26biw%3D1280%26bih%3D880%26tbs%3Disch:10%2C1417&um=1&itbs=1&iact=hc&vpx=483&vpy=534&dur=277&hovh=138&hovw=226&tx=86&ty=86&oei=kR-QTIevOYyjnQeV2Iy0DA&esq=3&page=3&ndsp=30&ved=1t:429,r:14,s:60&biw=1280&bih=880