by Douglas Messier
For billions of years, the surface of the Earth has been bombarded by unwanted cosmic visitors. Meteors, comets and asteroids have blasted massive holes in the surface of our planet, resulting in catastrophic climate change, mass extinctions and, according to one theory, the moon itself.
Early next month, the Earth will finally strike back. Japan’s Hayabusa2 spacecraft is preparing to bomb the asteroid Ryugu to obtain a sample from beneath the world’s rocky surface.
During the first week in April, Hayabusa2 is scheduled to launch the Small Carry-on Impactor (SCI) at Ryugu. SCI is composed of a disk impactor made of copper that will be deformed by an explosion into a semi-spherical shell that will penetrate the asteroid’s surface.
“The SCI impact enables us to conduct sampling from the interior of the asteroid, so the sample will be recovered from the floor of the artificial crater or the surrounding area covered with the ejecta from the SCI artificial crater,” according to a scientific paper on SCI.
“The artificial crater will produce a new fresh surface that is expected not to be significantly suffered from space weathering,” the paper stated. “In addition to sampling, remote sensing from the space craft will be able to refer this fresh surface in order to recognize the degree of space weathering on other surfaces and also observe the subsurface structure on the crater wall.”
This week, JAXA engineers have been conducting a “Crater Search Operation (Pre-SCI)” known as CRA1 to observe the area where SCI is likely to generate the crater. A similar operation will be conducted after the impact for comparison purposes.
“The CRA1 operation will take place between March 20 – 22, 2019,” JAXA said in a press release. “Descent preparation work will start on the 20th and the descent will begin from the 21st. Observations at the lowest altitude reached (approximately 1.7km) will be from the 21st to 22nd and the spacecraft will ascend on the 22nd. Figure 1 shows the site that will be observed.”
“Hayabusa2 begins its descent on March 21 at 08:57 JST (onboard time) with a speed of 0.4 m/s,” JAXA said. “On the same day at around 19:17 JST, the speed will be reduced to about 0.1 m/s. The spacecraft will continue to descend and reach the lowest point (altitude approximately 1.7km) on March 22 at around 03:32 JST and continuously observe at that altitude for a while.
Hayabusa2 will begin to ascend at 05:08 JST and return to the home position. Note that the times listed here are the planned values and the actual operation times may differ,” the space agency added.