Impactor

Appropriate impact conditions satisfying the angular momentum constraints of the Earth Moon system yield a Moon formed mostly from the mantles of the Earth and the impactor, while the core of the impactor accretes to the Earth.

Because the impactor is moving so rapidly, the rear of the object moves a significant distance during the short-but-finite time taken for the deceleration to propagate across the impactor.

Within moments the six-mile-wide chunk of rock, known as the Chicxulub impactor, caused tsunamis so large that the Great Plains were overwhelmed with water.

Hera will study Didymos and Dimorphos in the aftermath of the impact to see how it altered Dimorphos and better understand the effectiveness of the kinetic impactor technique.

A kinetic impactor – basically some sort of projectile that could knock the asteroid off its course, even if it didn’t destroy it altogether – could be used without leaving radioactive fallout, for example.

One possibility would use a single kinetic impactor; others might send out a scout spacecraft would would feed better information about the asteroid back down to Earth.

The two craft, initially stacked together, will separate with the reconnaissance craft hopefully reaching the asteroid first, and the impactor following through when details are collected.

As a result, the impactor is compressed, its density rises, and the pressure within it increases dramatically.

Computer simulations of this "late-impact" scenario suggest an impact angle of about 45° and an initial impactor velocity below 4 km/s.

Gilbert's calculations showed that the volume of the crater and the debris on the rim were roughly equivalent, so that the mass of the hypothetical impactor was missing, nor were there any magnetic anomalies.

In 2009, LCROSS sent a convert impactor into a permanently shadowed polar crater, and detected at least convert of water in a plume of ejected material.

In all but the smallest impacts this increase in temperature is sufficient to melt the impactor, and in larger impacts to vaporize most of it and to melt large volumes of the target.

In large impacts, as well as material displaced and ejected to form the crater, significant volumes of target material may be melted and vaporized together with the original impactor.

Many craters look as if the impactor fell into mud.

Many other shock-related changes take place within both impactor and target as the shock wave passes through, and some of these changes can be used as diagnostic tools to determine whether particular geological features were produced by impact cratering.

Small volumes of un-melted and relatively un-shocked material may be spalled at very high relative velocities from the surface of the target and from the rear of the impactor.

Stress levels within the shock wave far exceed the strength of solid materials; consequently, both the impactor and the target close to the impact site are irreversibly damaged.

Such events are generally so energetic that the impactor is completely destroyed, leaving no meteorites.

The current estimate of 300,000 tons for the impactor is only three-tenths of one percent of Barringer's estimate.

The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962.