{"id":2559,"date":"2019-02-18T08:49:28","date_gmt":"2019-02-18T06:49:28","guid":{"rendered":"https:\/\/www.e-astronomer.com\/?p=2559"},"modified":"2019-02-18T09:06:48","modified_gmt":"2019-02-18T07:06:48","slug":"esa-plans-mission-to-the-smallest-asteroid-ever-visited","status":"publish","type":"post","link":"https:\/\/www.e-astronomer.com\/?p=2559","title":{"rendered":"ESA plans mission to the smallest asteroid ever visited."},"content":{"rendered":"\n
ESA\u2019s planet-defending Hera mission will set a new record in space. The asteroid investigator will not only be the first spacecraft to explore a binary asteroid system \u2013 the Didymos pair \u2013 but the smaller of these two worldlets, comparable in size to Egypt\u2019s Great Pyramid of Giza, will become the smallest asteroid ever visited.\n

From afar, one asteroid looks much like another, until comparing them directly. Checking the well-known scale chart prepared by the Planetary Society of all asteroid and comets so far surveyed by spacecraft and the larger Didymos asteroid would form a modest dot, with its smaller moonlet struggling to make a single pixel.<\/p>\n

Didymos itself is just 780 m across \u2013 smaller than any asteroid visited by a probe other than the 350-m diameter Itokawa rubble pile visited by Japan\u2019s first Hayabusa spacecraft and the 500 m-diameter Bennu, around which NASA\u2019s Osiris-REx mission is currently in orbit.<\/p>\n<\/div>\n

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That leaves Didymos\u2019s orbiting moonlet \u2018Didymoon\u2019 as the smallest of all asteroids scheduled for robotic inspection, at just 160 m across.<\/p>\n

\u201cDidymoon\u2019s miniscule size really becomes clear when you look at other asteroids,\u201d comments Hera\u2019s lead scientist Patrick Michel, CNRS Director of Research of France\u2019s C\u00f4te d’Azur Observatory.<\/p>\n

Patrick also serves as co-investigator and interdisciplinary scientist on Japan\u2019s Hayabusa2 mission to the Ryugu asteroid, which is about 1 km in diameter: \u201cHayabusa2 images show a large boulder near the north pole of Ryugu \u2013 and that single boulder is about the same size as Didymoon in its entirety.\u201d<\/p>\n

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Its diminutive size was the reason Didymoon was chosen for a pioneering planetary defence experiment. In 2022, NASA\u2019s DART spacecraft will impact Didymoon in an attempt to change its orbit around its larger twin, to test the feasibility of asteroid deflection.<\/p>\n

\u201cThis isn\u2019t the first spacecraft impact into a planetary body,\u201d adds Patrick, \u201cNASA\u2019s Deep Impact crashed into comet Tempel 1 in 2005, but not to try and deflect it, instead it was to expose subsurface material \u2013 the 6-km diameter body was much too large. But Didymoon is small enough, and in a tight enough 12-hour orbit around its parent, that its orbital period can indeed be shifted in a measurable way.\u201d<\/p>\n

After the impact, Hera will survey the Didymos asteroids in 2026 to gather key information that will not be available from Earth-based observations, including Didymoon\u2019s mass, its surface properties and the shape of DART\u2019s crater.<\/p>\n<\/div>\n

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\u201cThis will give us a good estimate of the impact\u2019s momentum transfer, and hence its efficiency as a deflection technique,\u201d explains ESA\u2019s Hera project scientist, Michael K\u00fcppers. \u201cThese are fundamental parameters to enable the validation of numerical impact models necessary to design future deflection missions. We will better understand whether this technique can be used even for larger asteroids, giving us certainty we could protect our home planet if needed.\u201d<\/p>\n

Didymoon is very relevant for such testing as it is in the riskiest class of near-Earth asteroids because of its size: larger bodies can more easily be tracked, smaller bodies will burn up or do limited damage, while a Didymoon-sized impactor could devastate an entire region of our planet.<\/p>\n<\/div>\n

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Low-gravity worldlets<\/b><\/p>\n

The Didymos system is also attractive in terms of bonus science, offering insight into the formation of the binaries that make up around 15% of known asteroids.<\/p>\n

\u201cDidymos is spinning very swiftly, rotating once every two hours,\u201d says Patrick. \u201cAround its equator, its weak pull of gravity could be overcome by centrifugal force, potentially leading to material rising from the surface \u2013 the leading theory of where Didymoon came from. So landing on the equator would be impossible; you would have to touch down near its poles instead.<\/p>\n

\u201cDidymoon\u2019s small size means we know little about it, but we assume it would be spin-locked around its parent like Earth\u2019s moon, implying a slower spin equal to its orbital period. The plan is to land at least one CubeSat there, although it will require precise navigation to achieve this. The asteroid will have something like one millionth of Earth\u2019s gravity, with an estimated escape velocity of just 6 cm per second, so one danger might be bouncing back out to space.\u201d<\/p>\n<\/div>\n

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Patrick suggests Didymoon-class objects may additionally prove optimal for planned asteroid mining: larger bodies are comparatively rarer, while their smaller equivalents are more prone to fast spinning \u2013 caused by gradual warming due to sunlight.<\/p>\n

Hera is currently under study to be presented for approval by ESA\u2019s Space19+ Council meeting of European space ministers. It is planned for launch in 2023.<\/p>\n

Hera would be ESA\u2019s next mission to a small body after the Rosetta comet-chaser, benefiting from the expertise acquired during that 12-year mission. Long-term planning is crucial to realise future missions, and to ensure the continued development of innovative technology, inspiring new generations of European scientists and engineers.<\/p>\n<\/div>\n

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Science is everywhere at ESA. As well as exploring the Universe and answering the big questions about our place in space we develop the satellites, rockets and technologies to get there. Science also helps us to care for our home planet. All this week we’re highlighting different aspects of science at ESA. Join the conversation with #ScienceAtESA.<\/i><\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

ESA\u2019s planet-defending Hera mission will set a new record in space. The asteroid investigator will not only be the first spacecraft to explore a binary asteroid system \u2013 the Didymos pair \u2013 but the smaller of these two worldlets, comparable in size to Egypt\u2019s Great Pyramid of Giza, will become the smallest asteroid ever visited. … <\/p>\n","protected":false},"author":6,"featured_media":2557,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"footnotes":""},"categories":[183],"tags":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/www.e-astronomer.com\/wp-content\/uploads\/2019\/02\/Hera_at_Didymos_large.jpg","jetpack_shortlink":"https:\/\/wp.me\/paIt6s-Fh","_links":{"self":[{"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=\/wp\/v2\/posts\/2559"}],"collection":[{"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2559"}],"version-history":[{"count":2,"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=\/wp\/v2\/posts\/2559\/revisions"}],"predecessor-version":[{"id":2565,"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=\/wp\/v2\/posts\/2559\/revisions\/2565"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=\/wp\/v2\/media\/2557"}],"wp:attachment":[{"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2559"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2559"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.e-astronomer.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2559"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}