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Cassini's grand finale: ASU scientist comments on its discoveries

September 14, 2017

The spacecraft — whose mission ends Friday — showed us a dynamic Saturn, its 62 moons, and ice particles as large as office buildings

The Cassini space probe will end its mission early Friday morning. After 13 years orbiting Saturn, traveling some 4.9 billion miles total, Cassini will plummet into Saturn in a matter of minutes, vaporizing as it enters its atmosphere.

Arizona State University’s David Williams, an associate professor in the School of Earth and Space Exploration and a NASA supported scientist, knows Cassini well. While not a member of the Cassini Science Team, Williams supported the team in developing the concepts and techniques for making geologic maps of Saturn’s moon Titan from Cassini’s images. He has followed the Cassini mission since its beginning, and has worked with a number of Cassini scientists.

Question: What did we know about Saturn and its moons before Cassini? 

Answer: Prior to the Cassini mission, Saturn had been largely explored by Earth-based telescopes, and quick flybys from NASA’s Pioneer 10 and 11 (1970s) and by Voyager 1 and 2 (1980 and 1981) spacecraft. These missions showed some complexity existed in Saturn’s atmosphere and ring system, and that it had a series of heavily cratered icy moons with some surface variations. But those flybys did not provide detailed information about Saturn and its moons. So NASA began plans soon after the Voyager flybys to develop a Saturn orbiter mission, which became Cassini.

Q: How has Cassini redefined this view of Saturn and its moons?

A: The Cassini mission has greatly expanded our knowledge of how dynamic Saturn, its rings and its 62 moons are as planetary objects. Cassini has shown that Saturn has a very dynamic atmosphere similar to Jupiter’s, with giant storms that periodically erupt in its clouds. It has a dynamic northern polar region with an unusual hexagon-shaped cloud pattern surrounding a hurricane-like eye at its center. The storm is equivalent in size to four Earth’s.

Cassini showed that Saturn’s rings are composed of icy particles, some as large as office buildings, and some as small as smoke particles. Many of the small moons orbit within the ring plane, contort and distort the rings into dynamic patterns. And Cassini has shown that Saturn has geologically active moons. Two in particular, Titan and Enceladus, have altered our understanding of planetary objects. Both have liquid water oceans in their interiors. Enceladus erupts geysers of water vapor and organic materials from its south pole, and Titan has both wind-formed dunes and lakes and rivers formed by flowing methane.

Saturn's rings as seen by Cassini

Bright spokes and the shadow of a moon grace Saturn's B ring in this Cassini spacecraft image. Photo credit: NASA/JPL/Space Science Institute

Q: Why is this important to those of us on Earth?

A: Cassini has shown that Earth-like atmospheric and geologic processes are not restricted to the Earth, or Mars and Venus, but can occur on icy worlds and in the cold outer reaches of the solar system. It has shown that the ingredients for life can exist in more varied ways than we previously understood from studying the Earth alone, and it has expanded our understanding of the universe. 

Q: What is the legacy of the Cassini spacecraft? 

A: Cassini’s 13-year-long study of the Saturn system has set the stage for what’s next in planetary exploration. The knowledge gained, and the experience of the scientists and engineers has prepared them for the next major flagship mission to explore the outer solar system, the Europa Clipper mission, which will launch in 2022 to orbit and explore Jupiter’s icy moon Europa, which has a liquid water ocean underneath its icy crust. Faculty and students in ASU’s School of Earth and Space Exploration will be building instruments and analyzing data for that mission in the next decade and beyond.

Q: Are you sad to see Cassini go?

A: Yes, I am sad. It is always sad to see the end of an era of exploration. But new exploration awaits. With luck, Cassini’s discoveries will enable new missions back to Saturn, and new discoveries, in coming decades. 

Top photo: With this view, Cassini captured one of its last looks at Saturn and its main rings from a distance. Photo by NASA/JPL-Caltech/Space Science Institute

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5 things to know about the Constitution

Know your Constitution? 3/4 of Americans can't name all 3 branches of government
September 14, 2017

In honor of Constitution Day, ASU hosts events to promote understanding and appreciation of our nation’s fundamental law

Think Americans have a pretty firm grasp on the basics of U.S. government? Think again.

The annual Annenberg Constitution Day Civics Survey recently found that only a quarter of those surveyed could name all three branches of government. What’s more, more than a third couldn’t name any of the rights guaranteed under the First Amendment.

That’s troubling news to Peter McNamara, a professor of practice at Arizona State University's School of Civic and Economic Thought and Leadership (SCETL).

“[Those stats] mean for one thing that it is very hard for people with such limited political knowledge to participate meaningfully and constructively in civic debate,” he said. “Of course, another problem is the things that people think they know but are not actually true! I guess what these kinds of studies show is that there is a lot of work to be done on the civic education front.”

SCETL — launched in the spring — is rising to that challenge. On Thursday evening the school hosted its inaugural Constitution Day Lecture in the University Club on the Tempe campus to promote understanding and appreciation of our nation’s bedrock document. Clint Bolick, associate justice of the Arizona Supreme Court, delivered the lecture titled “The Renaissance of Federalism.” Watch highlights from the evening below:

Video by Ken Fagan/ASU Now

Earlier this week, SCETL kicked off its yearlong public lecture series “Free Speech and Intellectual Diversity in Higher Education and American Society.” And it will host another lecture from 1 to 2 p.m. Monday, Sept. 18, at Hayden Library to celebrate Constitution Day at ASU.

At Monday’s talk, titled “Hamilton and ‘Hamilton,’” McNamara will discuss the rivalry between Alexander Hamilton and Thomas Jefferson, as portrayed in the hit musical “Hamilton” (which comes to ASU Gammage in January). McNamara will pay special attention to each man's views on the Constitution.

To help beef up your constitutional cachet, here are five lesser-known facts about the historical document:

1. The Constitution was nearly not ratified

“Just as we have ‘battleground states’ and ‘safe states’ in our elections today, there were some less eventful state ratifying conventions (e.g., Delaware, New Jersey, Georgia, Connecticut), and others that were hotly contested (e.g., Pennsylvania, Massachusetts, New York, Virginia),” said Zachary German, SCETL assistant professor.

Rhode Island initially rejected passage of the Constitution, even refusing to send delegates to the Constitutional Convention. It took two and a half years before the state finally agreed to ratify, at which point it had already gone into effect.

In Pennsylvania, “Some delegates opposed to ratification were dragged from their boardinghouses to attend the vote in the state assembly (in Philadelphia) so that the assembly could meet its quorum,” said School of Politics and Global Studies Lecturer Tara Lennon. 

2. Why we celebrate Constitution Day on Sept. 17

This one’s pretty simple: The reason we have Constitution Day on Sept. 17 is because it was the last day the convention met in Philadelphia in the summer of 1787. That was the day all of the delegates still present stepped forward to sign their names with Gen. George Washington, who presided as the president of the convention.

3. The ‘pamphlet wars’ played a crucial role in ratification

“In the pamphlet wars over ratification, it was customary on both sides to use pseudonyms, such as ‘The Federal Farmer’ or ‘Publius,’ withholding authors’ identities in order to keep the focus on ideas and arguments, rather than personalities,” German said.

In a last-ditch effort to sway delegates in Virginia, the Federalist Papers were shipped down to the state, where Washington helped to reprint and distribute them — and it worked.

“It was really only a few votes that made the difference in Virginia,” said Paul Carrese, director of SCETL.

4. Memorable names took some convincing

Elbridge Gerry — the Massachusetts governor who approved a salamander-shaped state senate district to favor his political allies, thus giving rise to term “gerrymander” — was originally famous for being one of three delegates who at the end of the convention refused to sign. And even John Hancock — the man with the most famous, iconic signature on the Declaration of Independence — was opposed to ratification as late as January 1788.

Both men eventually voted in favor of it; Hancock doing so after assurances were made regarding the promise of the first 10 amendments, and Gerry after taking the advice of leading delegates such as Benjamin Franklin and Washington who pleaded with delegates to swallow their particular objections and support the larger good achieved by the new frame of government. Gerry later served in the U.S. House and as vice president under James Madison.

5. George Washington thought we should be thankful for it

According to McNamara, on Oct. 3, 1789, Washington issued a proclamation that Nov. 26, 1789, be designated a day of Thanksgiving to God for the “favorable interpositions of his providence, which we experienced in the course and conclusion of the late war, for the great degree of tranquility, union, and plenty, which we have since enjoyed, for the peaceable and rational manner, in which we have been enabled to establish constitutions of government for our safety and happiness, and particularly the national one now lately instituted, for the civil and religious liberty with which we are blessed.”