Won­drous en­coun­ters

The achieve­ments of the twin Voyager craft are a space tri­umph that nearly wasn’t.

The Star Malaysia - Star2 - - INSIGHT - By ED­WARD C STONE By AMINA KHAN

THE Voyager 1 space­craft is the first hu­man-made ob­ject to ven­ture into in­ter­stel­lar space. Even if de­fined only by dis­tance, the Nasa/Jet Propul­sion Lab­o­ra­tory twin Voy­agers are Amer­ica’s great­est space ad­ven­ture. They’ve been fly­ing suc­cess­fully for more than 36 years and are bil­lions of kilo­me­tres from home. What isn’t widely known is that they al­most never made it out there.

The first pro­posed mis­sion in the late 1960s was for four space­craft to take ad­van­tage of a rare align­ment of the four outer plan­ets of the So­lar Sys­tem; Jupiter, Saturn, Uranus and Nep­tune would all be on the same side of the sun. How­ever, in De­cem­ber 1971, Nasa de­cided it couldn’t af­ford the bil­lion-dol­lar pric­etag for a 12-year “grand tour” mis­sion with four space­craft.

This align­ment hap­pens only ev­ery 176 years, and the next launch op­por­tu­nity was just five years away, in 1977. To avoid miss­ing the op­por­tu­nity, JPL en­gi­neers quickly de­vised a plan to send two sim­pler space­craft on fouryear flights to Jupiter and Saturn, with the hope of con­tin­u­ing on to Uranus and Nep­tune.

But ex­plor­ing space is hard. If some­thing breaks, you can’t send out a me­chanic. Be­cause of the hours it takes ra­dio sig­nals to travel to the space­craft, ground con­trollers can’t fix any­thing in real time. So JPL en­gi­neers had to build the smartest space­craft yet de­signed, us­ing “fault pro­tec­tion” soft­ware in their small com­put­ers to spot any prob­lems and take ac­tion.

The au­ton­omy of the two space­craft was es­sen­tial to their ca­pa­bil­ity and longevity, but that also made it dif­fi­cult dur­ing the first few months to learn how to fly them.

Voyager 1 was on a shorter, faster tra­jec­tory, so Voyager 2 was launched first, on Aug 20, 1977. Soon af­ter launch, Voyager 2’s fault pro­tec­tion was put to the test. The space­craft was tum­bling and in a state of me­chan­i­cal ver­tigo. The com­puter be­gan ex­chang­ing pri­mary sys­tems for back­ups, fol­low­ing its fault­pro­tec­tion se­quences.

Al­though some en­gi­neers wanted to re­boot the com­puter, a key en­gi­neer re­alised that a WHEN fac­ing on­com­ing flood­wa­ters, ants use their help­less ba­bies as float­ing life-pre­servers – by stick­ing them at the very bot­tom of the life-rafts that they build with their own bod­ies.

The find­ings, de­scribed in a paper pub­lished in PLOS One, re­veal that ant rafts have a fas­ci­nat­ing in­ter­nal struc­ture – one that max­imises the group’s buoy­ancy and thus, their chances of sur­vival. But it puts the young ant brood at the very bot­tom of the boat, ex­posed to hun­gry fish and the risk of drown­ing.

“It was an in­ter­est­ing con­tri­bu­tion. No one had re­ally looked at this idea of the brood as a flota­tion de­vice,” said David Hu, a me­chan­i­cal en­gi­neer at the Ge­or­gia In­sti­tute of Tech­nol­ogy, who was not in­volved in the study. “It adds a level of so­phis­ti­ca­tion to the rafts that was pre­vi­ously not un­der­stood.”

Re­searchers have long mar­velled at the in­cred­i­ble or­gan­is­ing pow­ers of ant colonies. Like bee­hives and ter­mite nests, these so-called su­per-or­gan­isms ex­hibit what’s known as “swarm in­tel­li­gence”, able to act quickly in co­or­di­nated ways.

Ants may be tiny alone, but they’re a for­mi­da­ble foe in large num­bers. They build bridges with their bod­ies that oth­ers can then walk over, they sur­round in­trud­ers and “microwave” them to death with their body heat, and when a flood hits, they can link up and form “rafts” that can float to higher, drier ground. One study even found that the in­va­sive fire-ant Solenop­sis in­victa ac­tu­ally traps air pock­ets to form a pro­tec­tive layer that helps keep them afloat.

But re­searchers at the Univer­sity of Lau­sanne in Switzer­land won­dered if there was even more com­plex or­gan­i­sa­tion to these ant rafts. Af­ter all, who were the un­lucky ants forced to the bot­tom of the raft? Was there a rea­son they were cho­sen for the job? Were they sub­merged un­der­wa­ter, and thus at higher risk of drown­ing?

The re­searchers also won­dered whether the ants would place the most valu­able or vul­ner­a­ble mem­bers, like the queen and the young brood, away from the wa­ter. The queen is im­por­tant be­cause she’s the mother of the colony, and the brood – made up of young ants in lar­val or pu­pal form, un­able to fend for them­selves and can’t re­ally move around on their own and likely re­quire ex­tra pro­tec­tion. re­set would be fa­tal be­cause Voyager 2’s sun sen­sor had to lo­cate and lock onto the Sun to ori­ent it­self. The en­gi­neers ner­vously watched the data as the space­craft righted it­self and sta­bilised. As some­one put it, Voyager 2 was “smarter than we were”.

Two weeks later, Voyager 1 had its own launch ad­ven­ture but rode it out in bliss­ful ig­no­rance. The first-stage rocket un­der­per­formed, re­quir­ing a longer burn by the sec­ond

To test their hy­poth­e­sis, the sci­en­tists went to Formica selysi ant colonies along the bank of the Rhone River and picked up a bunch of worker ants, brood ants and queens. They took them back to the lab, put them in groups of 60 work­ers with queens and gave some of them 10 young brood ants to care for. That’s when they started to slowly raise the wa­ter level, and watched how these mini-colonies re­acted.

Sure enough, the worker ants placed the queen in the cen­tre of the ant raft, pro­tected from the wa­ter on all sides. But, to their sur­prise, the ants took the young, help­less brood – the lar­val and pu­pal ants – and lined their bod­ies along the base of the raft, where they would be most ex­posed to the wa­ter.

This seemed coun­ter­in­tu­itive; shouldn’t the ants try to pro­tect their young? Af­ter sub­merg­ing both adult ants and their brood young in the wa­ter, the sci­en­tists found that the pu­pae and lar­vae were ac­tu­ally more buoy­ant than the adults.

This played out in the over­all suc­cess of the brood­bot­tomed rafts, which seemed to do bet­ter than rafts held to­gether only by adult worker ants. Once the rafts dis­em­barked, the ant rafts with no brood took less time to dis­as­sem­ble, but they had more “non-re­spon­sive” work­ers that needed re­viv­ing, the au­thors found.

The rafts with brood, on the other hand, took a lit­tle more time to dis­as­sem­ble, but there were far fewer on their crew who needed CPR.

There were a few caveats, Hu pointed out: For ex­am­ple, their lab rafts were far smaller than those in the wild, which can carry a whole colony of 100,000 or so mem­bers. And 10 brood for 60 adults was a pretty high ra­tio for an ant colony, he added.

Still, the re­search gives in­sight into how ants play to each of their mem­bers’ strengths. The adult ants link jaws to limbs and move around to give the raft its struc­ture; the brood can’t move, but their buoy­ant bod­ies (per­haps be­cause they have more fat con­tent, Hu said) help keep ev­ery­one afloat.

The ant young seemed to suf­fer no long-term ill ef­fects from be­ing put to work like this, the re­searchers found. They suc­cess­fully reached adult­hood at the same rate as brood that weren’t rafted. – Los Angeles Times/ McClatchy-Tri­bune In­for­ma­tion Ser­vices stage to achieve the speed needed to reach Jupiter at the pre­scribed time. It did the job with only 3.5 sec­onds of fuel left; if it had run out of fuel, it would have been late for its ren­dezvous with Jupiter.

Won­drous en­coun­ters with Jupiter en­sued in 1979. Thanks to the space­crafts’ cam­eras, the Voy­agers let ev­ery­one marvel at Jupiter’s or­ange moon Io as it spouted eight vol­canic plumes, re­veal­ing it as the most ge­o­log­i­cally ac­tive ob­ject in the So­lar Sys­tem.

En­coun­ters with Saturn in 1980 and 1981 en­tranced us with im­ages of its ma­jes­tic rings and many moons. Sci­en­tists knew that its planet-size moon Ti­tan had an at­mos­phere, but they didn’t know it was mainly ni­tro­gen and much denser than Earth’s.

In 1981, the con­tin­u­a­tion of the Voyager jour­ney be­yond Saturn, as well as Nasa’s other plan­e­tary pro­grammes, were in dire dan­ger of can­cel­la­tion. But, aware of strong pub­lic in­ter­est buoyed by the il­lu­mi­nat­ing im­ages and un­ex­pected dis­cov­er­ies, the White House agreed to con­tinue the plan­e­tary pro­gramme and Voy­agers’ mis­sion to Uranus.

Five years later, Voyager 2 flew past Uranus. Fi­nally, in 1989, Voyager 2 reached Nep­tune, find­ing its winds among the fastest and strong­est even though it’s the far­thest from the heat of the Sun.

Be­fore Voyager 1’s cam­eras were turned off (to save power and mem­ory), they looked back to­ward the Sun, tak­ing a pho­to­graph of tiny Earth in the black dis­tance, the famed “pale blue dot”.

With­out the Voyager mis­sion, we wouldn’t have been able to see the di­ver­sity and splen­dour of our So­lar Sys­tem up close, to an­swer that haunt­ing, per­sis­tent ques­tion, “What is it like out there?” The ad­ven­ture that al­most didn’t hap­pen will con­tinue as Voyager 2 joins Voyager 1 in ex­plor­ing the space be­tween the stars, un­til about 2025, when power runs out. They will jour­ney on, car­ry­ing golden records, which are time cap­sules of Earth where their great ad­ven­ture be­gan. – Los Angeles Times/ McClatchy-Tri­bune In­for­ma­tion Ser­vices

Ed­ward C Stone, a for­mer di­rec­tor of Nasa’s Jet Propul­sion Lab­o­ra­tory, is the project sci­en­tist of Nasa’s Voyager mis­sion and a pro­fes­sor of physics of Cal­tech. WHEN stars ex­plode, it’s a messy but use­ful busi­ness, the mas­sive blasts seed­ing the uni­verse with such key el­e­ments like cal­cium, iron and ti­ta­nium.

And with the help of a new high-en­ergy X-ray te­le­scope, Nasa said last week that as­tronomers are closer than ever to see­ing just what’s go­ing on.

“This is help­ing us un­tan­gle the mys­tery sur­round­ing how stars ex­plode,” said Fiona Har­ri­son, prin­ci­pal in­ves­ti­ga­tor on NuS­TAR, or the Nu­clear Spec­tro­scopic Te­le­scope Ar­ray.

Com­bined with im­ages from an­other Nasa X-ray ob­ser­va­tory, Chan­dra, NuS­TAR has cre­ated the “first ever map of ra­dioac­tive ma­te­rial in the rem­nants of a star that ex­ploded”, she told re­porters.

One of the big­gest sur­prises was that stars, which are spher­i­cal ob­jects, do not ex­plode in a cir­cu­lar man­ner, she said.

Rather, it ap­pears that the blast is more lumpy and dis­torted from the very be­gin­ning.

“Prior to the ex­plo­sion, the core of the star lit­er­ally sloshed about,” said Har­ri­son, a sci­en­tist at the Cal­i­for­nia In­sti­tute of Tech­nol­ogy.

As­tronomers based their find­ings on the ob­ser­va­tions of Cas­siopeia A, or Cas A for short, a rem­nant of a su­per­nova 11,000 light-years away.

The star ex­ploded around 350 years ago, blow­ing off outer lay­ers with an ex­treme heat that cre­ated even more el­e­ments.

Cas A has been ex­pand­ing since the year AD1670, pro­pel­ling de­bris at a speed of about 16 mil­lion kilo­me­tres an hour, but never be­fore have sci­en­tists been able to glimpse the ra­dioac­tiv­ity that was pro­duced in­side the ex­plo­sion.

“With NuS­TAR, we have a new foren­sic tool to in­ves­ti­gate the ashes left be­hind when this star ex­ploded,” said Brian Grefen­stette, an as­tronomer at Cal­tech.

NuS­TAR launched in 2012 on a two-year mis­sion, join­ing the Nasa fleet that also in­cludes the Hub­ble Space Te­le­scope.

It is the first or­bit­ing te­le­scope to fo­cus on the high-en­ergy X-rays of the elec­tro­mag­netic spec­trum.

Al­though the Chan­dra Ob­ser­va­tory re­mains the world’s most pow­er­ful X-ray te­le­scope, NuS­TAR can mon­i­tor a range the older or­bit­ing te­le­scope can’t see.

Robert Kir­sh­ner, an as­tronomer at the Har­vard-Smith­so­nian Cen­ter for As­tro­physics, de­scribed the ra­dioac­tiv­ity map NuS­TAR pro­duced as “pi­o­neer­ing sci­ence”.

“You should care about this,” said Kir­sh­ner, who was not in­volved in the project.

“Stars per­form a kind of alchemy where they turn one el­e­ment into an­other. The Earth it­self is some­thing that is the residue of this as­tro­nom­i­cal process.”

Star ex­plo­sions played a key role in the iron used to make cars, the cal­cium in our bones and the ti­ta­nium used to man­u­fac­ture hip re­place­ments, he ex­plained.

“So we are all star dust and NuS­TAR is show­ing us where we came from, in­clud­ing our re­place­ment parts.” – AFP

Lonely trav­eller: With­out the Voyager mis­sion, the world would not have been able to see the di­ver­sity and splen­dour of the So­lar Sys­tem up close, or an­swer that haunt­ing, per­sis­tent ques­tion: ‘what is it like out there?’ — Filepic

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