The Density of the Medusae Fossae Formation: Implications for its Composition, Origin, and Importance in Martian History
L. Ojha and K. Lewis, JGR-PLANETS 2018
Please follow the follow link for an excellent summary of this work:
Seasonal Slumps in Juventae Chasma, Mars
L. Ojha et al., JGR-Planets 2017
- Dark topographic slumps several meters wide, tens of meters in length and up to a meter in depth are observed on the slopes of Juventae Chasma (JC), Valles Marineris (VM), Mars.
- The slumps are seasonal features: Over the course of three Mars years, ten active slumps have been observed in JC, all of which formed in or near the coldest time of the year.
Association with RSL?: These slumps usually originate near the terminal points of recurring slope lineae (RSL), once RSL have faded.
Association with atmospheric phenomenon?: Low-altitude atmospheric obscurations, with H2O ice, confined within the topography of VM and JC are also observed when the slumps form.
Formation mechanism?: The presence of atmospheric obscurations with H2O ice near times when the slumps form is intriguing, but no direct evidence currently exists to support that they aid in slump formation. Further monitoring of this site will help establish if RSL and/or atmospheric events play a role in the creation of contemporary slumps.
These are images from the MARCI camera showing low-alitude atmospheric obscuration inside Valles Marineris (VM) and Juventae Chasma (JC) of Mars. In some cases, H2O ice clouds are observed inside the VM and JC.
In 2011, my undergraduate adviser (Alfred McEwen) and I noticed dark, narrow streaks on Mars that are now known as Recurring Slope Lineae (RSL). RSL are observed to form and grow during the warmest time of the year. RSL are gravity driven process in that they are observed to form on very steep slopes (25-35 degrees). McEwen, I and several others published our initial finding on RSL in 2011 (link).
From 2013-2015, I wrote three papers (Ojha et al., 2013; Ojha et al., 2014; Ojha et al., 2015) that significantly contributed to our understanding of Recurring Slope Lineae on Mars. Perhaps, my greatest contribution was the discovery of hydrated salts on the RSL slopes, which suggest that water plays a key role in their formation. The RSL season is about to start on Mars again, and we are planning an in-depth investigation with CRISM and HiRISE to learn more these enigmatic features on Mars.
I have used my extensive knowledge of planetary remote sensing to contribute to many other projects. You can find other involvements in my publication list.
My first few undergraduate projects were geophysics and seismology related. As one of the Southern California Earthquake Center (SCEC) intern, I spent my sophomore-summer and significant part of that year later involved in a seismology project taking a look at triggered tremors (link).
In 2012, as I was walking from the department of geosciences to lunar and planetary lab, I met Jay Quade, and he approached me with a question that I had not really thought about. Jay had been working in Atacama desert where he saw large boulder fields that were the result of active seismicity (see Google Earth figure below). Jay and I looked at similar boulder fields on Moon and Mars and concluded that at least few of the boulder fields on both Moon and Mars could have also formed from similar processes (link).
I am involved in NASA's InSight mission to understand the formation and evolution of terrestrial planets. InSight will arrive on Mars in 2018, and will consist of a seismometer, a heat-flow probe and a rotation tracking instrument. I have been working to understand the expected heat-flow at the landing site based on variety of gravity and topographic analyses (link)
Landscape evolution: cosmogenic nuclide
An integral part of understanding our cosmos is understanding our own backyard. I had an early exposure to the geology of the Himalayas, and have always found the origin and the evolution of Himalayas fascinating. Ken Ferrier from Georgia Tech and I have started a project to understand the evolution of Himalayas in the far-west Nepal. This part of Nepal is seismically very active and also gets a lot of rain during the annual Monsoon season. We expect this region to have high erosion rates due to seismically induced landslides, avalanches, and rainfall (see NASA TRMM data below).