The first of 22 weekly dives between Saturn's rings has been completed
It marks the first time a man-made object has explored this region of space
NASA’s Cassini spacecraft has begun an unprecedented series of space dives that will see it plunge through the icy rings of Saturn, in the final phase of its 20-year mission.
Controllers operating the Deep Space Network antenna in Goldstone, California confirmed data collected during its passage was being received from the probe just after 8:00 a.m. GMT (3:00 a.m. ET) on Thursday.
“In the grandest tradition of exploration, NASA’s Cassini spacecraft has once again blazed a trail, showing us new wonders and demonstrating where our curiosity can take us if we dare,” said Jim Green, director of the NASA’s Planetary Science Division in a statement.
Plunging through the ring plane on Monday morning, scientists had taken precautions to protect the spacecraft from unexpected collisions with tiny smoke particles by using its dish-shaped antenna as a shield.
This meant repositioning Cassini’s antenna away from Earth, which caused controllers to temporarily lose signal with the unmanned probe.
“We could only rely on predictions, based on our experience with Saturn’s other rings, of what we thought this gap between the rings and Saturn would be like,” said Earl Maize, Cassini project manager at NASA’s Jet Propulsion Laboratory.
“I am delighted to report that Cassini shot through the gap just as we planned and has come out the other side in excellent shape.”
A roaring success
The unprecedented gap-run was the first of 22 weekly dives Cassini will undertake between April and September, traveling at a top speed of more than 76,800 mph (120,000 kph).
As it zipped through the gap, the probe traveled to within 1,900 miles (3,000 kilometers) of Saturn’s cloud tops (where air pressure is similar to the atmospheric pressure of Earth at sea level), and within about 200 miles (300 kilometers) of the innermost visible edge of the rings, NASA said.
Now that engineers have reacquired the probe’s signal, they will evaluate data from this first dive and make tweaks to the orbit and trajectory to ensure the craft is protected ahead of future dives.
During these final revolutions around Saturn – which take around seven days – Cassini will return pioneering scientific data which scientists hope will help them decipher how giant planets evolve.
It will also collect a wealth of information including detailed maps of Saturn’s gravity and magnetic fields, which could answer questions surrounding the speed of Saturn’s rotations.
The closing plunges of the mission could also reveal the makeup and origin of the rings, as well as providing intriguing glimpses of the gas giant from closer than ever before.
“The spacecraft is now on a ballistic path, so that even if we were to forgo future small course adjustments using thrusters, we would still enter Saturn’s atmosphere on September 15, no matter what,” said Earl Maize, Cassini project manager at NASA’s Jet Propulsion Laboratory (JPL), in a statement.
Shortly before impact, Cassini will emit a final signal which will be received on Earth just over an hour later.
Why destroy Cassini?
Cassini’s mission has twice been extended – in 2008 and 2010 – but the probe is now running low on rocket fuel.
Before Cassini’s mission, little was known about the planet. Previous missions, including Pioneer 11 and Voyagers 1 and 2, all undertook flybys providing glimpses of Saturn and yielding ground-breaking discoveries.
But it was Cassini’s first close-up survey of the planet and its system of rings and moons in 2004 that changed scientists’ understanding of the planet and altered our approach to future planetary exploration.
10. First complete view of the north polar hexagon and discovery of giant hurricanes at both of Saturn's poles. Saturn's polar regions have surprised scientists with the presence of a long-lived hexagonal-shaped jet stream in the north and hurricane-like storms at both poles. The driving forces of each remain a mystery.
9. Mystery of the dual bright-dark surface of the moon Iapetus solved. The origin of Iapetus' two-faced surface has been a mystery for more than 300 years. The Cassini spacecraft solved the puzzle, showing that dark, reddish dust in Iapetus' orbital path is swept up and lands on the leading face of the moon.
7. Vertical structures in the rings imaged for the first time. Once about every 15 years, the sun shines on the edge of the ring plane and northern and southern sides of the rings receive little sunlight. Cassini measured the thick, long shadows from this rare event to determine the heights of structures within the rings.
6. Radio-wave patterns shown not to be tied to Saturn's interior rotation as previously thought. Saturn emits radio waves known as Saturn Kilometric Radiation. A similar radio wave pattern was measured at Jupiter to deduce the length of that planet's day. However, it was discovered that the variation in radio waves controlled by the planet's rotation is different in the northern and southern hemispheres. The northern and southern rotational variations also appear to change with the Saturnian seasons and the hemispheres have actually swapped rates. Saturn's length of day is still not known.
5. Studies of the great northern storm of 2010-2011. In 2010 Cassini got a front-row seat to a massive storm that disrupted Saturn's relatively tranquil atmosphere. The largest temperature increases recorded for any planet were measured. Molecules never before seen in Saturn's upper atmosphere were detected. The storm diminished shortly after its head collided with its tail, a little less than a year after it began. Saturn's rings are seen as the thin blue line in this image, due to the filters used to show methane absorption. The rings are outside the atmosphere, and therefore are not affected by methane absorption.
NASA/JPL-Caltech/University of Arizona/University of Idaho
Cassini's top 10 discoveries about Saturn —
4. Titan revealed as Earth-like world with rain, rivers, lakes and seas. Titan is the only known place in the solar system, other than Earth, that has stable liquid on its surface. Rather than water, its lakes are made of liquid ethane and methane.
3. Saturn's rings revealed as active and dynamic. Cassini's mission allowed scientists to observe changes in Saturn's dynamic ring system, including what could be the birth of a moon. The disturbance, visible in the lower left of this image, is thought to be an icy body migrating out of the ring, believed to be part of the process required to form a moon.
2. Icy plumes on Saturn's moon Enceladus. Here, the plumes can be seen back-lit by the sun. The discovery was such a surprise that the mission was completely reshaped to get a better look. Evidence of water-based ice in the plume excited scientists further, as life as we know it relies on water.
1. The Huygens probe makes first landing on a moon in the outer solar system. The Huygens probe's historic landing in 2005 was the most distant to date. In addition to providing this photo, the probe found the moon to be similar to Earth before life evolved, with methane rain, erosion, drainage channels and dry lake beds.