February 2021 | Letter from the Directors
Looking for life on Mars
This newsletter was written the day after many of us sat mesmerized and slightly terrified watching NASA land another rover on Mars in the continuing quest to find out if our neighbor planet was once habitable and inhabited. Once we could breathe again after hearing the news that Perseverance was sitting safely on the Martian surface, our thoughts turned to the wonders of what will be found by the rover and its reconnaissance helicopter Ingenuity.
For those of you who have been watching the investigation of Mars for long enough, you will remember that an early debate was whether Mars ever had water on its surface. The debate started with the first close-up images of Mars taken by numerous Soviet and American spacecraft in the 1960’s and 70’s that showed what looked very much like topography carved by flowing water. Jumping ahead to Jezero crater, the landing site for Perseverance, which is described as a former lake with river delta deposits, we can safely assume that the debate over whether there was once surface water on Mars has been resolved.
What has not yet been resolved is whether life developed during this window when Mars’ surface may have been habitable. The first experiments to detect life that were included on the Viking lander in the late1970’s returned what seemed to be positive results, but the debate continues about whether those results proved the presence of a respiring Martian microbe or instead just reflected unusual chemical properties of the Martian soil.
Perseverance landed at a site where the geology suggests the kind of place you would want to live if you were a Martian microbe and indeed shares a similar age and examples of the mineralogy seen in ALH 8400—the meteorite from Mars that was purported to contain life in 1996. Whether or not life ever existed in this river delta is the question that will consume Carnegie scientists Andrew Steele and Pamela Conrad for the next several years.
Both are members of the numerous science teams connected to the Perseverance mission and indeed Steele along with Lindy Elkins-Tanton were part of the team that defined the science and format of the Perseverance mission leading to sample return. Steele and Conrad are co-investigators on the SHERLOC instrument intended to search for organic compounds in the Jezero surface.
This time around, however, whatever data that can be obtained remotely by the rover will eventually be checked in laboratories back on Earth, including those at EPL, when the samples collected by Perseverance are returned to Earth in the next decade. For now, we will have to be satisfied (meaning “jump for joy”) about the news that some samples from the Ryugu asteroid returned to Earth by the Japanese Hyabusa2 are likely to make an appearance at EPL later this year to be analyzed by EPL staff scientist Larry Nittler and colleagues including George Cody and Dionysis Foustoukos.
Far far away or deep beneath your feet
The research reported by EPL in February once again demonstrates the huge range of scales covered by our efforts. Scott Sheppard’s discovery of a large object in the outer Solar System, which he nicknamed “FarFarOut”, has now been confirmed as the most distant object ever observed in our Solar System. At 132 AU (just shy of 20 billion miles) FarFarOut just slightly outdoes another object discovered by Scott and colleagues, FarOut, which orbits at 124 AU in the vast reaches of the nearly empty outer Solar System.
At the other extreme, EPL’s Yingwei Fei, Asmaa Boujibar, and Peter Driscoll along with a number of collaborators subjected small samples of bridgmanite, the high-pressure form of the common mineral enstatite, to pressures as high as 12 million atmospheres and temperatures to 7200 K. Their goal was to understand the properties of bridgmanite—a common rock-forming mineral in the deep interior of a super-Earth sized planet. Bridgmanite is likely the most common mineral in Earth’s lower mantle (670 to 2900 km).
Super-Earths are planets about 1.5 to 2 times larger than Earth. Planets of this size are not found in our Solar System but are among the most common size planet found around other stars in the Milky Way. The team used the world’s most powerful pulsed-power machine, Sandia’s Z Pulsed Power Facility, to shock their samples to extreme pressures and temperatures to explore the physical state and melting temperature of materials deep in a super-Earth. The work—done on samples only a few millimeters in size—provides key information on the physical state of these planets that can be used to address whether they might be capable of creating and sustaining magnetic fields. Planetary magnetic fields are often considered as a necessary ingredient for a planet to sustain life on its surface as the fields deflect the energetic particles associated with solar and cosmic rays.
Lectures to our neighbors around the world
We are pleased to announce the schedule for the Spring 2021 Neighborhood Lecture Series, which will remain virtual for the time being. The first lecture will be held on March 18, 2021. EPL Staff Scientist Alycia Weinberger will give a talk entitled, “Come not between the dragon and his wrath: A tale of small stars and their planets”. The presentation will focus on Weinberger’s recent work with former postdoc Meredith MacGregor who explored how our nearest stellar neighbor, Proxima, might be giving a hard time to its close-in planet Proxima b.
Then on April 29, former DTM postdoc and now Canada Excellence Research Chair at the University of Alberta, Graham Pearson, will be talking about his work with diamonds and what they can tell us about how the Earth works. Both lectures begin at 6:30 pm eastern time. The lectures are free to the public, but pre-registration is requested.
A Closer Look at EPL
Beginning next month, our newsletter will take on a new look. Each month we will focus on one of the six broad research areas we pursue on campus. We will cover what our scientists consider to be the most important questions they are investigating and provide an opportunity for our scientists to answer questions from the public on these research themes. We also will give you a closer look at the people at EPL carrying out this work and the paths they took to careers in science. We hope that you like this new format!
Rick and Mike
Director and Deputy Director
Earth and Planets Laboratory