We're NASA Mars scientists. Ask us anything about today's news announcement of liquid water on Mars.

From my fourth grade students (edited by me for clarity):

Could there be Martian life in the water since it's only there at certain times of the year? What might happen to the life when the water disappears?

It was mentioned that there's life on Mars in the form of microbes on the machinery. Is it possible that these microbes sent by us could harm Martian life?

Thank you!

It's possible. We know of forms of life that hibernate during dry seasons on Earth. The water that we're seeing within the RSL (the seasonal dark streaks that we're seeing on slopes on Mars) is salty. Salty water could be harmful to life.

We don't know what Earth life could do to any potential life on other worlds. That's why we try to clean our spacecraft very carefully. -- LT

What's the next step?

The next step is to look for more locations where brine flows may occur. We have covered 3% of Mars at resolutions high enough to see these features. -RZ

I read that the rover can't approach specific areas (including where the streaks are located) due to risk of infection by Earth microbes.

What are some examples of microbes that could be living on the rover that you are concerned with infecting the surface of mars?

These features are on steep slopes, so our present rovers would not be able to climb up to them. Because liquid water appears to be present, these regions are considered special regions where we have to take extra precautions to prevent contamination by earth life. Our current rovers have not been sterilized to the degree needed to go to an area where liquid water may be present. -RZ

If the rovers haven't been properly sterilized already, will this throw doubt upon any possible future discovery of Mars-based microbes living in or near the water? Wouldn't detractors be able to claim that they are microbes that somehow survived from Earth?

The rovers have been sterilized for their particular landing sites where there's been no evidence of present day liquid water. To go to the RSL rovers will be required to be sterilized to a higher level. We also take samples of microbes that might be on the spacecraft before they're launched, so we can compare with any future discoveries. -RZ

How long into the future do you think it will be before we can realistically think about sending humans to Mars?

Presently, NASA is looking into the possibility of sending humans to the vicinity of Mars in the early 2030s. In this scenario, the earliest humans to the surface would be in the late 2030s. -RZ

What quantity of water are we talking about? what volume?

We think this is a very small amount of water -- maybe just enough to wet the top layer of the surface of Mars. The streaks are ~4-5 meters wide and ~200-300 meters long. -- LT

How much liquid water are we talking about? Like.. tap water leaking when you don't close the valve tight enough, or Niagara falls?

Tap water leaking. -RZ

It was shown back in 2011 that salt water flows may be a seasonal occurrence. What was the final proof for the team that this was happening, and what was your initial reaction to the data?

With MRO, we were able to observe a few of these sites at various points within the Mars year, and again the next year. Over time, we saw that the streaks darkened and lengthened during the warm season and faded during the cold season. A benefit of having MRO lasting so long is that we're able to see changes and patterns over time.

My reaction? This is all very exciting! The closer we look at Mars, the more interesting it gets. -- LT

Is NASA now considering putting a man on Mars to get more data on this or can we find all the information without having a man/woman on Mars?

They've been considering putting someone on Mars for a long while.

https://www.nasa.gov/content/nasas-journey-to-mars/

NASA is developing the capabilities needed to send humans to an asteroid by 2025 and Mars in the 2030s – goals outlined in the bipartisan NASA Authorization Act of 2010 and in the U.S. National Space Policy, also issued in 2010.

The basic answer is yes, NASA is planning to send humans to Mars in the 2030s. It's always helpful to have more information before sending them, and that's why our robotic explorers are so important. -- LT

Do any of the space scientists at NASA write poetry/do art? If their art is inspired by their scientific work, can you please share it with us?

Absolutely. It takes all kinds of creative minds to do science and engineering that no one has ever done before. Among our mission teams, you'll find actors, musicians, sculptors, painters -- the list goes on. For visual artists, two individuals who spring to mind are Bill Hartmann (http://www.psi.edu/about/staff/hartmann/painting.html) and Dan Goods (http://www.directedplay.com/). -- SLS

Is there any evidence of evaporation happening on mars? And do you know where this water came from?

Thanks for your time!

New impact craters on Mars sometimes have bright ice exposed in the bottom of the crater. This goes away over a few months. The ice, when exposed, is going from solid to vapor. Evaporation of a briny flow will also occur, so the water needs to be resupplied. We don't know how. -RZ

What does this mean in regards to possible life?

We think liquid water is essential for life (at least as we know it.) That does not mean that life is there; but, it's a good place to look. -RZ

what would be the procedure, if life is found on Mars? would the public be made aware? who gets told first?

Information flows to the public very quickly. If one of our missions here at JPL detected life, we'd notify NASA headquarters immediately, who would then follow procedures to notify the US government and the public. -- SLS

If the Mars rover were to travel to the site of the briny water, what would be the scientific procedure for determining if that water supports life?

The Curiosity rover does not have life detection instruments. It would look for confirmation that liquid water was present and how long during the day it was liquid. -RZ

This may be a bit far-future looking, but does the fact that we know liquid flowing water exists mean anything for terraforming Mars in the future?

Think of this as a "seep" not a flow. We have not seen flowing water on the surface. We see something that darkens the soil, which may be just a wetting action but still involves (briny) liquid. -RZ

In the articles I've read so far, the water is referred to as "briny" and that it's more fluid than it is water. What does that mean? Would this be something theoretically possible to drink or grow things with? Or would this be the kind of thing that would need purification before it could be used?

The salts in the water appear to be perchlorates, so I wouldn't want to drink the water. To be a future resource for humans, you would want to remove the salts. -RZ

briny means salty. I don't know if they mean 'salt' like on earth, where it's just table salt, or some other type of 'salt'.

But briny water means salty water.

The salts detected on Mars are magnesium or sodium perchlorate. These are not typical salts on the Earth, but they have the attribute that they can keep water liquid to much colder temperatures which occur on Mars. -RZ

Congratulations! Given the seasonal nature of today's discovery, does this suggest that their is a hydrologic cycle on Mars?

There is a hydrologic cycle on Mars, but typically it involves vapor going to ice (frost) or ice going to vapor. There is no rain in Mars today, but there may have been very early in its history. -RZ

What will the next generation of robots we send to Mars look like? Now that there's this new evidence will that change what testing equipment gets a space onboard? What's the food like at the cafeteria at NASA?

We are planning to send the InSight lander to Mars in 2016, which will be lander designed to detect Mars-quakes. We also have a rover in development for the 2020s (same basic design as MSL/Curiosity) and NASA is considering the science that might fly on the next Mars orbiter to be launched sometime after the 2020 rover.

The instruments that are chosen to fly are selected because they can accomplish the science goals of the mission, so as the science goals change - with new discoveries - instruments will be proposed and selected accordingly.

The food at JPL is actually quite good! Wood-fired pizza, burgers, sandwiches, good salad bar, etc. --LT

First off congratulations on such an amazing discovery.

Second, how close is the rover to the water? Will you be able to get close enough to get pictures without contamination?

There are no confirmed brine flows (RSL) near Curiosity nor Opportunity. There are in Gale Crater some interesting slope streaks but they are several km away from the Curiosity's present path. -RZ

Scale of 1-10, how excited does this make you guys? Is this a huge deal for the scientific community?

This is super exciting! It is an important discovery because it is evidence that supports our hypothesis that the RSL (seasonal dark streaks that appear to flow in the warm season) are flowing briny (salty) water. --LT

Hello NASA,

What do you say to those who would argue we already had proof with the ice caps? Obviously, they're full of water. Don't they melt periodically?

Sincerely, A fan.

The ice caps freeze and sublime (solid to vapor.) The RSL water stays liquid because it has salts in it. Yes, we know there's water on Mars. We're looking for where it stays liquid for an extended period of time. -RZ

what was the hardest technical challenge you faced on this project?

what was the hardest nontechnical (political, cultural, legal, emotional &c) challenge?

The features that darken and fade as temperatures get warmer and then colder are long but narrow. The difficulty was to get enough resolution from our orbiter instruments to first detect, and then characterize what these features are. Mars Reconnaissance Orbiter (MRO) can do that with its HiRISE camera and CRISM Mineral Mapper. -RZ

Why should the average joe care about this? What does this mean for science and space exploration?

Liquid water, even if very salty, is still a good place to look for life forms. We don't know how robust martian life (if it exists) could be. Also, water in any form is a resource that future missions could exploit. -RZ

With the discovery of water on Mars does that mean there could be rainbows on Mars?

Not quite rainbows, because there is no rain, but we have seen icebows with the Pathfinder mission. -- RZ

This seems to indicate that mars is closer to the end of its life cycle than a younger planet like Earth (as in, a long while ago mars had flowing water, oceans, and likely life.. now it's mostly arrid) What are your thoughts on that? I can hardly fathom what kind of life may have once been on Mars - but it's kind of depressing to think that it is something that was once but unless terraforming becomes a thing - Mars will remain a grave stone of a world where life once may have thrived.

Mars had liquid water on its surface billions of years ago. Where that water went is the subject of our current investigations. Was it lost to space? Or is it frozen in the crust today? Mars seems to have ice ages when water at the poles is sublimated and redistributed to the rest of the planet. Ice in the crust today may have been formed during one of those ice age cycles. -RZ

Where does the water come from? I understand that water vapor is very low in the martian atmosphere, yet surely there must be a sizable partial pressure of water vapor in order to hydrate the salts.

We don't know where the water in these hydrated salts come from. That is the next mystery to solve! They leading hypotheses are that (1) the salts are sucking up the water from the atmosphere, but you are correct, there isn't much water in the atmosphere, and (2) that the water is coming from the subsurface. There is certainly more to learn! --LT

This is gonna sound silly, but what does it taste like?

It would be salty, but considering that perchlorate is toxic to humans, you wouldn't want to drink it. -- SLS

About how much longer do you think it will take to get visuals of the rest of Mars at a high enough resolution to see these types of things?

MRO has been taking data at Mars since March 2006, nearly 10 years. The HIRISE instrument (high-resolution imager) has currently taken images of only about 2.4% of the surface. --LT

Serious question, why is this a surprise considering there's evidence of ice and glaciers? From what I saw when I googled it mars can get warm enough to melt ice, so what's to say this isn't from the glaciers melting and then refreezing?

The RSL are a surprise because they appear to flow seasonally and the best hypothesis is due to liquid, briny water. Mars can get barely above freezing for short periods above time. The RSL are not though to be due to glaciers because where they are seen (equatorial and mid-latitude regions) we do not see glaciers. --LT

Awesome news! Really excited about this!

How long before you guys can map a significant area (~20%) of Mars with Hi-Res images?

MRO has been in orbit for 10 years and has mapped ~2.4 percent of Mars in high-res. We have six-meter-per-pixel imagery of more than 90 percent of the surface. -- LT

How long has water been on surface of Mars?

Water in some form has probably been on Mars since at least 3.9 Bya. --LT

What procedures does NASA have in place to prevent potential contamination of these active water sources on Mars?

We have a policy for Planetary Protection. This policy means that we clean our spacecraft of earth microbes to varying degrees depending on where the spacecraft is being sent. It the intended location is thought to have a high possibility of harboring microbes, then we go to the maximum extent to clean the spacecraft. --LT

Is this water we're taking about, or could it be another liquid?

The signature that was seen by the MRO CRISM experiment was hydrated perchlorates. This means that water (H2O) was involved. --LT

Will 2016 mars mission aim to explore more on this?

No. The 2016 NASA Mars mission, InSight, will put a seismometer on Mars to measure Mars-quakes. --LT

If the atmospheric pressure on surface is the same as Earth's, but the air composition is the same as well as the soil/terrain, how likely would we be seeing streams or ponds of liquid water there?

If the atmospheric pressure on Mars was the same as on Earth, then conditions are warm enough that water could be liquid on many places. The atmospheric pressure may have been greater in the past when the Mars channels were formed. -RZ