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Mars rover Curiosity makes first gravity-measuring traverse on the Red Planet

January 31, 2019

ASU graduate student is on a team that found Mars rocks less compacted, more porous than scientists expected

A clever use of nonscience engineering data from NASA's Mars rover Curiosity has let a team of researchers, including an Arizona State University graduate student, measure the density of rock layers in 96-mile-wide Gale Crater.

The findings, to be published Feb. 1, in the journal Science, show that the layers are more porous than scientists had suspected. The discovery also gives scientists a novel technique to use in the future as the rover continues its trek across the crater and up Mount Sharp, a three-mile-high mountain in its center.

"What we were able to do is measure the bulk density of the material in Gale Crater," said Travis Gabriel, a graduate student in ASU's School of Earth and Space Exploration. He worked on computing what the grain density should be for the rocks and ancient lakebed sediments the rover has been driving over.

"Working from the rocks' mineral abundances as determined by the chemistry and mineralogy instrument, we estimated a grain density of 2810 kilograms per cubic meter," he said. "However, the bulk density that came out of our study is a lot less — 1680 kilograms per cubic meter."

The much lower figure shows that the rocks have a reduced density, most likely resulting from the rocks being more porous. This means the rocks have been compressed less than scientists have thought.

Like a smartphone, but better   

The engineering sensors used in the study were accelerometers, much like those found in every smartphone. In a phone, these determine its orientation and motion. Curiosity's sensors do the same, but with much greater precision, helping engineers and mission controllers navigate the rover across the Martian surface.

But while the rover is standing still, the accelerometers also measure the local force of gravity at that spot on Mars.

The team took the engineering data from the first five years of the mission — Curiosity landed in 2012 — and used it to measure the gravitational tug of Mars at more than 700 points along the rover's track. As Curiosity has been ascending Mount Sharp, the mountain began to tug on it, as well — but not as much as scientists expected.

"The lower levels of Mount Sharp are surprisingly porous," said lead author Kevin Lewis of Johns Hopkins University. "We know the bottom layers of the mountain were buried over time. That compacts them, making them denser. But this finding suggests they weren't buried by as much material as we thought."

Making Mount Sharp

Planetary scientists have long debated the origin of Mount Sharp. Mars craters the size of Gale typically have central peaks raised by the shock of the impact that made the crater. A central peak would account for part of the mound's height. But the uppermost layers of the mound appear to be made of wind-scoured sediments more easily eroded than rock. Where did they come from?

And did these sediments once fill the entire bowl of Gale Crater? If so, they might have weighed heavily on the materials at the base, compacting them.

But the new findings suggest Mount Sharp's lower layers have been compacted by only a half-mile to a mile (1 to 2 kilometers) of material — much less than if the crater had been completely filled.

"There are still many questions about how Mount Sharp developed, but this paper adds an important piece to the puzzle," said Ashwin Vasavada, Curiosity's project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, which manages the mission. "I’m thrilled that creative scientists and engineers are still finding innovative ways to make new scientific discoveries with the rover."

Gabriel added, "This is a testament to the utility of having a diverse set of techniques with the Curiosity rover, and we’re excited to see what the upper layers of Mount Sharp have in store."

Top photo: In a selfie taken in mid-January 2019, Mars rover Curiosity prepares to enter a new, clay-mineral-rich unit on its traverse up Mount Sharp in Gale Crater. Mission scientists are anxious to see what a new gravity-measuring technique will reveal about the mountain and Gale Crater's history. Image credit: NASA/JPL-Caltech/MSSS

Robert Burnham

Science writer , School of Earth and Space Exploration

480-458-8207

ASU Law professor leading campaign to help reduce child drownings in Arizona


January 31, 2019

When Di Bowman was making the move from Michigan to Arizona, she had found just the right home. But there was one flaw, and it was a deal-breaker.

“We landed here in Arizona, we had a house without a fence around the pool, and I refused to move in,” she said. “I had a 1-year-old at the time, and I refused to move in until we had a barrier up there.” Di Bowman and Coach Bowman Di Bowman and Coach Bowman. Download Full Image

It was the start of a mission for Bowman, a professor at the Sandra Day O’Connor College of Law and the School for the Future of Innovation at Arizona State University. She began researching and discovered that child drownings are a preventable public health crisis in the United States and globally — and that the problem is particularly acute in Arizona.

According to the World Health Organization, drowning is the third-leading cause of unintentional injury death globally, and the highest drowning rates are among children 1 to 4 years old.

In the United States, drowning is the leading cause of unintentional death among 1- to 4-year-olds, according to the USA Swimming Foundation. And Arizona has the second-highest drowning rate in that age category, behind only Florida.

There are clear divisions among socioeconomic and racial demographics. A USA Swimming Foundation study found that 79 percent of children in households with incomes less than $50,000 have little or no swimming ability. Further, 64 percent of African-American children, 45 percent of Latino children and 40 percent of Caucasian children have little or no ability to swim.

Bowman is now leading a multifaceted, multipartner campaign to help safeguard all children in Arizona, especially those in the highest risk categories. The campaign is gaining momentum, focusing on better ordinances and wider access to swim lessons. But the first step was raising awareness.

‘It’s not in people’s consciousness’

Bowman applied for a grant with a private foundation but was turned away, being told that it wasn’t a significant enough public health issue.

She cited the statistics, underscoring Arizona’s dubious distinction of having the second-highest drowning fatality rate for children 1 to 4 years old, with 4.45 deaths per 100,000 children. And she pointed to research suggesting the numbers are even higher, and that the deaths are, for the most part, preventable and due to lack of supervision, the absence of proper barriers and adults severely overestimating the swimming ability of children. But it was to no avail.

“I was horrified, given these stats,” she said. “It’s a huge issue, but it’s not talked about, it’s not in people’s consciousness. Unless you’ve had a drowning in your family or you know somebody socially who has been impacted by a fatal or nonfatal submersion event, people just don’t think about drowning as being an issue.”

She knew there needed to be greater awareness. So she enlisted the help of experts at Phoenix Children’s Hospital and a high-profile resource within the ASU community: Sun Devils swimming and diving coach Bob Bowman, the Team USA coach who helped guide Michael Phelps to a record-breaking Olympic career.

Bob Bowman is no relation to Di Bowman. In fact, the two had never before met. But when she asked for his help in producing a public service announcement, he did not hesitate.

“As someone who works around pools every day, I appreciate the need for safety and appropriate supervision of all participants,” Bob said. “Toddlers and children must be under constant supervision around water and we should strive to equip all children and parents with water safety skills.”

The public service announcement won a media award from the Drowning Prevention Coalition of Arizona. And it also caught the attention of the Phoenix-based Hubbard Family Swim School, who reached out to Di to partner with ASU on a multifaceted drowning prevention program designed to reduce drowning-related mortality and morbidity in Arizona generally, and in the 1- to 4-year-old range in particular. A pillar of their partnership is to better provide access to swimming lessons. Now, they are leading efforts within ASU and Hubbard Family Swim School to partner with the city of Phoenix to build a state-of-the-art indoor swimming pool in the Maryvale section of Phoenix, an area of the city where drowning rates are especially high.

“The idea is to bring a pool to the people who are more likely to drown and give them that as a resource,” said Di, who added that the facility would use the curriculum taught at the Hubbard Family Swim School locations throughout the Valley.

She said Maryvale’s demographics, including greater poverty rates and a higher percentage of minority and refugee residents, correlate with higher drowning risks.

“Families are less likely to be able to pay $80 a month to put a child in weekly swim lessons,” she said. “Moreover, the absence of an indoor public swimming pool in the city of Phoenix creates a huge access barrier to families with limited transportation options. In short, many of these families simply cannot access a facility in which their children can have year-round lessons.”

Seeking stronger ordinances

Di Bowman hails from Australia, a country with a more stringent culture of pool safety.

“I think it is fair to say that Australia is a nanny state when it comes to public health,” she said. “Local governments have implemented stringent laws requiring, for example, private pools to be equipped with a free-standing barrier and self-locking pool gates. And that’s complemented with a comprehensive public education campaign spearheaded by former Australian Olympic swim coach Laurie Lawrence. This collective effort to address childhood drownings appears to be a huge factor in reducing mortality and morbidity rates in Australia."

And she said Australian officials are much more proactive in enforcing those regulations.

“To the point that they use various forms of aerial surveillance devices to photograph houses with backyard pools and spas, and if the photos suggest that the pool or spa is not fenced, action will be taken by the council to have the owners install a fence that meets the regulatory requirements.”

She does not advocate that level of intrusiveness. But she says the evidence is undeniable that barriers around pools reduce child drownings, and she would like to persuade local governments to review — and, where necessary, revise — existing pool barrier ordinances to ensure they meet best practices. Working with ASU Law library staff and research assistants, Bowman is mapping every ordinance in Arizona, showing the correlation between laxer local ordinances and higher drowning rates.

“We know what best practice looks like in terms of barrier ordinances, and we’ve got the data to prove it,” she said. “So we’re hoping to use this data, which is being visually mapped using Geographical Information System mapping techniques, to show mayors the importance of local ordinances in protecting some of the most vulnerable in our community — our children. This work builds on the phenomenal work that so many people in Arizona have undertaken in order to reduce drowning fatalities in our backyard. And collectively I hope that this research will result, over time, in the strengthening of local ordinances and a reduction in the number of childhood deaths we have each year here in Arizona.”

Lauren Dickerson

Marketing and communications coordinator, Sandra Day O’Connor College of Law

480-965-7636