Vac­uum! A-ah! Saviour of the uni­verse

Dr Michelle Dick­in­son, cre­ator of Nanogirl, is a nan­otech­nol­o­gist who is pas­sion­ate about get­ting Ki­wis hooked on sci­ence and en­gi­neer­ing. Tweet her your sci­ence ques­tions @medick­in­son

Weekend Herald - - Science & Tech -

Fly­ing a space­craft, catch­ing up with an as­teroid, then fly­ing along­side that as­teroid with­out crash­ing into it is — to put it mildly — a chal­leng­ing ac­tiv­ity. Amaz­ingly, this week, Nasa’s Osiris-Rex probe si­dled up along­side a di­a­mond-shaped as­teroid known as Bennu and is do­ing just that.

Osiris-Rex stands for Ori­gins, Spec­tral In­ter­pre­ta­tion Re­source Iden­ti­fi­ca­tion, Se­cu­rity-Re­golith Ex­plorer. By un­der­stand­ing how as­ter­oids like Bennu fly and how their tra­jec­to­ries are shaped, the re­searchers hope to im­prove pre­dic­tion mod­els for as­teroid im­pact fore­casts — just in case one of those large space rocks is set on a course to­wards Earth.

Nasa’s first as­teroid-sam­pling mis­sion, Osiris-Rex has this week ar­rived at its desti­na­tion. It has been chas­ing the 500m-wide rock for the past 27 months and has cov­ered two bil­lion kilo­me­tres in the process.

Now that it’s caught up with the as­teroid, it will fly along­side it for the next four weeks map­ping its sur­face and study­ing the rock’s com­po­si­tion. After that, the probe will scout the sur­face for the best place to try to col­lect a sam­ple.

The goal is to col­lect a sam­ple of the as­teroid and trans­port it back to Earth for in-depth sci­en­tific anal­y­sis. Hope­fully, by July 2020 the per­fect lo­ca­tion will have been found and sam­ple col­lec­tion will be able to take place.

Rather than land on the as­teroid, the plan is to “tap” the as­teroid with a long arm. The arm, known as the Touch-and-Go Ac­qui­si­tion Mech­a­nism (Tagsam), will then vac­uum at least 60g — but po­ten­tially up to 2kg — of the as­teroid’s re­golith, the near­est equiv­a­lent to what we on Earth would re­fer to as top­soil.

This Tagsam vac­u­um­ing process will be in­cred­i­bly fast, tak­ing just five sec­onds to com­plete — al­most like an in­ter­plan­e­tary high five. Fol­low­ing the trans­fer, Osiris-Rex will stay close to Bennu un­til March 2021, be­fore re­turn­ing to Earth some­time in 2023.

As­ter­oids are left­overs from the orig­i­nal build­ing blocks of the so­lar sys­tem, which means that they hold the clues to events that cre­ated the sun and the plan­ets. The goal,

through anal­y­sis of the re­golith ma­te­rial, is to bet­ter un­der­stand the ini­tial days of the so­lar sys­tem, as well as to ex­am­ine the role that car­bon­rich as­ter­oids like Bennu might have played in the emer­gence of life on Earth and pos­si­bly other plan­ets.

There are some fas­ci­nat­ing com­pli­ca­tions in­volved in ma­noeu­vring in close prox­im­ity to an as­teroid like Bennu, which will be­come the small­est ob­ject ever or­bited by a probe.

The as­teroid’s rel­a­tively small size and low mass mean that it’s grav­i­ta­tional field is in­suf­fi­ciently strong for the probe to en­ter a tra­di­tional or­bit — Nasa’s sci­en­tists are hav­ing to de­velop new tech­niques to re­main in close prox­im­ity to the rock for the du­ra­tion of the mis­sion.

Fur­ther com­pli­cat­ing mat­ters, the heat of the sun on the side of the space­craft will cause the probe to emit ther­mal en­ergy — that emis­sion will change the probe’s tra­jec­tory ever so slightly — all of which needs to be fac­tored into the con­troller’s cal­cu­la­tions.

Data from this mis­sion will be in­valu­able to the grow­ing space econ­omy of which as­teroid min­ing is still a goal. There is a large eco­nomic in­cen­tive to de­ter­mine the best way to try to mine raw ma­te­ri­als from as­ter­oids for use in space for con­struc­tion and fu­elling rather than hav­ing to launch these ma­te­ri­als from earth or even for bring­ing back to earth if we use up all of our read­ily avail­able re­sources.

For now, we house­hold chore avoiders should take note — an in­ter­plan­e­tary vac­uum cleaner may be about to change the world.

Pho­tos / Getty Im­ages, AP

Osiris-Rex Sam­ple Re­turn Mis­sion chief sys­tems en­gi­neer Tim Linn points to the arm of the space­craft on a model that will vac­uum up a sam­ple of ‘top­soil’ off the Bennu as­teroid (in­set).

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