A new NASA mission, called the Double Asteroid Redirection Test (DART) mission due for launch this summer, aims to launch a spaceship that will directly punch an asteroid. Motherboard reports: The mission's target is an asteroid system called Didymos, which contains two space rocks that orbit each other. In late 2022, DART will forcefully impact the smaller asteroid in this system, a tiny moon called Dimorphos, so that scientists can assess the feasibility of knocking any space rocks that threaten Earth off course in the future. [...] DART will pioneer a subtler form of planetary defense, in which the trajectory of an asteroid is changed by a very small amount that becomes significant over time. Late next year, the mission will crash into Dimorphos at about seven kilometers per second. Shortly before the collision, the spacecraft will deploy a small satellite provided by the Italian Space Agency that is tasked with watching "the mess we make," [said Andy Rivkin, a planetary astronomer at the Johns Hopkins University Applied Physics Laboratory and the investigation team lead for DART]. Observations from the Italian satellite, as well as from powerful telescopes on Earth, will reveal just how much Dimorphos was affected by the crash. Rivkin and his colleagues expect the change in orbital speed to be small -- about one millimeter per second -- which would add up to a shortening of the orbital period by about 10 minutes. But even this very slight shift would be enough to redirect the trajectory of a hazardous asteroid that threatened Earth, provided scientists have a lead-time of a decade or two before the projected impact.

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