Thursday, April 27, 2017, 10:19 AM - Cassini survived! NASA's probe put its handlers through 22-hours of terror as it made its closest pass over Saturn yet, plus, three comets make close flybys of Earth, and two missions update how our Sun interacts with the Milky Way. It's What's Up In Space!
Remember back in August 2012, when NASA's Curiosity rover plunged into the Martian atmosphere, bound for a sky-crane descent to the surface of the Red Planet? Recall that the team back on Earth was going to be on the edge of their seats, as the time delay between Earth and Mars forced them into a situation they called "7 Minutes of Terror" - when they received words in the Jet Propulsion Laboratory control room that Curiosity was at the top of the atmosphere, the rover would have actually been on the surface by then for a period of 7 minutes... either scattered across the landscape in pieces due to a failed attempt, or just sitting there, patiently waiting for orders from Earth.
Well, NASA's Cassini spacecraft, in orbit around Saturn, did a one-up on Curiosity. On Wednesday, April 26, at around 5 a.m. ET, the probe dove directly between the planet's upper cloud layers and the inner edge of its vast ring system. The next opportunity to hear Cassini check in after that maneuver, however, was at 3 a.m. ET on Thursday, April 27.
So, the team here on Earth went through 22 hoursof terror, as they waited and hoped that this amazing mission was able to continue, on track, until it reaches its scheduled end, a little less than five months from now.
Now, the chances of Cassini actually striking something large enough to damage it, as it crossed the plain of the rings, was very small. There's was over a 99 per cent chance that it would be perfectly fine. However, even a small chance had to be causing some stress in the mission team.
As of Thursday morning, it all paid off, as the raw photos below were posted to the NASA Jet Propulsion Laboratory Instagram account, among them, the closest look ever at Saturn's atmosphere, including its north polar hurricane.
What are the top discoveries that Cassini has given us about Saturn, its rings and its amazing collection of moons?
Before Cassini arrived at Saturn, we knew of 43 moons that circle the gas giant and its rings. Since the the spacecraft began its investigation of the Saturn system, in 2004, that number has jumped to a total of 62 confirmed moons, and 2 more that are unconfirmed. Cassini itself is credited with finding 7 of those moons, plus four tiny moonlets in the planet's A ring, and both of the unconfirmed moons.
In addition, the spacecraft has sent back the closest images we've ever seen of Saturn's full complement of moons, showing off the surface and clouds of Titan, the amazing landscapes of Tethys, Dione, Mimas, Rhea and Enceladus, and the incredible variety represented in the smaller satellites.
Astronomers have caught glimpses of Saturn's north polar hexagon before, but Cassini revealed it in its full splendor.
Not only that, but the probe zoomed in on the hurricane raging at the planet's north pole, returning infrared images that NASA scientists used to put together this false-colour image, to show off the details of its clouds.
This storm measures around 2,000 kilometres across, or roughly the size of Typhoon Tip, from here on Earth in 1979, but Saturn's storm has winds blowing in it up to 540 kilometres per hour. The strongest winds measured in a tropical cyclone here were 345 km/h, in Hurricane Patricia, in the eastern Pacific, in 2015.
Prior to Cassini arriving at Saturn, Jupiter's Europa was all the rage when it came to our search for life elsewhere in the solar system.
Now, in 2017, Saturn's icy moon, Enceladus, is gaining ground in our search for extraterrestrial life, as there is ample evidence of not only a global subsurface ocean beneath the moon's frozen crust, but also hydrothermal vent activity - the same as we can find at the bottom of Earth's oceans!
As Cassini pulled into orbit around Saturn, it detached a small probe by the name of Huygens, which plunged into the atmosphere of Titan, deployed a parachute and settled down onto Titan's surface to give us our first views from this frigid, hydrocarbon moon.
The above video may start off as computer graphics, just to give some context, but it soon switches over to actually imagery sent back from Huygens, on its descent to the surface. Wow!
By looking out into space with telescopes and examining data from the Voyager probes as they speed away from our solar system, scientists have constructed a particular model for how our Sun's magnetic field - known as the heliosphere - interacts with the interstellar space that surrounds us.
A new look at the Voyager data, with help from the Cassini spacecraft, is presenting a new, updated picture, though.
According to NASA, when charged particles from the Sun - either from the solar wind or in a coronal mass ejection - attempt to exit the heliosphere, some of them get kicked back into the solar system, becoming neutral and picking up a considerable amount of speed in the process. One of Cassini's instruments is tuned to detect these particles, and from the timing of when the particles arrive at the spacecraft, compared to when they are emitted by the Sun, it gives an idea of the size and shape of the heliosphere.
So, that implies that the shape of the heliosphere is fairly even, all around the solar system, thus it's more like a sphere (the left view, above), rather than having an elongated tail trailing behind the solar system (the right view, above) as we move through the galaxy.
"This data that Voyager 1 and 2, Cassini and IBEX provide to the scientific community is a windfall for studying the far reaches of the solar wind," Arik Posner, the Voyager and IBEX program scientist, who was not involved with this study, said in a NASA statement. "As we continue to gather data from the edges of the heliosphere, this data will help us better understand the interstellar boundary that helps shield the Earth environment from harmful cosmic rays."