The threat of a collision is reinforced by the existence of huge craters such as the Meteor Crater (also known as Barringer Crater) near Flagstaff, Arizona, U.S.A.
यह प्रत्यक्ष ख़तरा एक महत्त्वपूर्ण कारण है कि क्यों वैज्ञानिक ग्रहिकाओं का अध्ययन करते हैं ।