Active Stocks
Mon Dec 04 2023 15:47:26
  1. Power Grid Corporation Of India share price
  2. 212.9 1.21%
  1. Reliance Industries share price
  2. 2,421 1.15%
  1. State Bank Of India share price
  2. 594.65 3.99%
  1. HDFC Bank share price
  2. 1,609.05 3.44%
  1. Tata Steel share price
  2. 130.95 0.77%
Business News/ Opinion / Columns/  Cosmic curio: A little bit of Bennu
Back Back

Cosmic curio: A little bit of Bennu

OSIRIS-REx travelled over 6 billion km in space to reach Bennu and get back to earth

(From left) Lockheed Martin mission operations assurance lead Graham Miller, recovery specialists Michael Kaye and Levi Hanish prepare the sample return capsule from Nasa’s Osiris Rex mission for transport after it landed at the US department of defence’s Utah test and training range on 25 September. (AP)Premium
(From left) Lockheed Martin mission operations assurance lead Graham Miller, recovery specialists Michael Kaye and Levi Hanish prepare the sample return capsule from Nasa’s Osiris Rex mission for transport after it landed at the US department of defence’s Utah test and training range on 25 September. (AP)

NEW DELHI : Half a century ago, astronauts brought back a total of a few hundred kilograms of rocks from the moon. It generated great excitement, because this was the first extraterrestrial material humans ever examined. There have been meteor strikes, of course. But the moon rocks were the first such stuff that humans deliberately brought onto our planet.

This week, another haul of extraterrestrial rocks landed on the earth. Not from the moon, though. These were from an asteroid called Bennu that is, right now, motoring along about 82 million km from the earth. To put that in perspective, the moon is nearly 400,000 km away; the sun, about 150 million km. That 82 million km figure should flag another difference from the earlier haul: unlike the moon rocks, those from Bennu were not collected and brought home by humans.

Instead, it was a spacecraft named OSIRIS-REx. My last column reminded you of another meeting between spacecraft and asteroid. That was DART, which smashed into Dimorphos a year ago. I assure you, OSIRIS-REx’s encounter with Bennu was far less violent.

As I wrote in this space in 2020 (And yet she pirouettes, there above Bennu,, OSIRIS-REx spent two years finding its way to Bennu. Once there—it was about 300 million km distant at that point—it spent two more years flying alongside, and in orbit around Bennu. For much of that time, through hundreds of orbits around the asteroid, it was examining Bennu, searching for the right spot on the surface from where to pick up asteroid-material.

Eventually, the craft chose an area that Nasa called “Nightingale": a patch of something resembling sand, surrounded by rocks. OSIRIS-REx descended till a long extended arm with a cup at its end touched that sand. It set off a small controlled explosion designed to deposit some of the surface material into the cup. Then the craft slowly withdrew and returned to its orbit.

Of course, this was just the start. Earthbound scientists were not likely to be satisfied with simply filling that cup with sand and rubble and letting it stay out there in space. They wanted to study this primordial material of our universe—older than anything here on earth. They wanted to bring it back to earth.

And three years on from the encounter with Bennu, they managed to do just that. A few days ago, a canister the size of a mini-fridge landed in a remote part of Utah in the US. Inside it is OSIRIS-REx’s treasure: a bit of Bennu.

How did this happen? Well, over these last three years, OSIRIS-REx has been shooting through space towards us, carrying that capsule with rubble from Bennu. According to Nasa, when it got sufficiently close to the earth, the scientists and engineers on the project held a meeting in which they asked and offered answers to a number of questions. From a Nasa report, here’s some of that: “Are projections showing that the capsule will land in its target area? Yes. Do the latest predictions of peak heat and peak deceleration levels that the spacecraft will endure still meet our expectations? Yes. Is the spacecraft ready to release the capsule and divert itself away from earth? Yes. Is the team ready for the day? Yes. Is the range clear? Yes."

So: when it was within about 100,000km of the earth’s surface, OSIRIS-REx released the capsule. It coasted through space for a few hours. It entered earth’s atmosphere last Sunday morning, travelling high above California at 36 times the speed of sound. At some point, it deployed parachutes to slow its descent.

Thirteen minutes after entering, black from barrelling through the atmosphere, it landed in Utah.

In a photo taken just minutes later, the capsule sits upright on a flat stretch of desert, surrounded at a respectful distance by a few bushes, the bright orange parachutes lying on one side. It’s almost like a staged photo, capsule set just so on the sand.

But of course it isn’t staged.

Looking at the scene, it is almost mind-numbing to think of everything that preceded this near-perfect touchdown. The long voyage to Bennu: because of its intricate path, the craft travelled about 3 billion km over the years it took to reach. Settle into orbit around Bennu. The months of observing the surface. The long-armed gentle touch to gather material off the asteroid. Deposit the material in a canister and seal it for the long voyage back: another 3 billion km and three years. Release the capsule into the earth’s atmosphere, where it heats up to 5,000°C as it descends. Slow it enough that it lands undamaged.

Think, too, of the elaborate instructions that OSIRIS-REx had to be programmed with. Because how can you control this craft in real-time, when—at its furthest from earth—it takes 18 minutes for an instruction to travel to OSIRIS-REx and another 18 minutes for an acknowledgement or confirmation to travel back?

And even so, a monumental mission like this had its moments of minute, delicate manoeuvres as well.

For example, on 10 September the spacecraft was about 7 million km from the earth, travelling at about 23,000 kmph. It fired its thrusters briefly, enough to change its speed by less than 1 kmph. Without this minute correction, it would have soared past the earth.

All this, to deliver that little bit of Bennu—about 250 gm—to scientists who can’t wait to examine it.

And having dropped off the capsule, what happens to OSIRIS-REx? It fired its thrusters again and has set course for the asteroid Apophis, and has now been renamed OSIRIS-APEX. Its aim, though, is not to gather more material. Apophis is on a path that will bring it to within 30,000 km of the earth in 2029. Nasa says OSIRIS-APEX will “enter orbit of Apophis soon after the asteroid’s close approach of earth to see how the encounter affected the asteroid’s orbit, spin rate, and surface".

Takes my breath away. All in all, I can’t help thinking how lucky I am—we are—to live in a time of so many close encounters of the asteroid kind.

Once a computer scientist, Dilip D’Souza now lives in Mumbai and writes for his dinners. His Twitter handle is @DeathEndsFun.

Milestone Alert!
Livemint tops charts as the fastest growing news website in the world 🌏 Click here to know more.

Catch all the Elections News, Business News, Market News, Breaking News Events and Latest News Updates on Live Mint. Download The Mint News App to get Daily Market Updates.
More Less
Updated: 28 Sep 2023, 11:21 PM IST
Next Story footLogo
Recommended For You
Switch to the Mint app for fast and personalized news - Get App