MARS Frequently Asked Questions

Methane emissions from human sources (including the energy, waste, and agricultural sectors) drive about 30% of today’s global warming. Because methane is a greenhouse gas over 80 times more powerful than CO2 but remains in the atmosphere for far less time, emission reductions now can deliver immediate climate progress and buy us time to pursue broader decarbonization.

Reducing methane emissions also carries significant benefits for public health, economic livelihoods and energy security. 

A report from the International Energy Agency, UNEP, and the Climate and Clean Air Coalition finds that in the fossil fuel sector alone, where reductions are overwhelmingly cost-effective and readily available, targeted action could avert nearly 1 million premature deaths from ozone pollution, 90 million tonnes of crop losses and about 85 billion hours of lost labor from heat exposure by 2050, all while providing roughly USD 260 billion in direct economic benefit.

The Methane Alert and Response System (MARS) is a data-to-action platform set up as part of the UNEP International Methane Emissions Observatory (IMEO) mission to put open, reliable, and actionable data into the hands of those who can reduce emissions. UNEP announced it at the 27th United Nations Climate Change Conference. 

MARS uses satellites to scan the globe for major emission sources and alerts countries and companies so that they can take methane action and accelerate progress supporting the implementation of the Paris Agreement and Global Methane Pledge.

Through MARS, notifications of detected emissions events are shared directly with governments and, if possible, facility operators who are members of UNEP’s Oil and Gas Methane Partnership 2.0 (OGMP 2.0). 

Governments may nominate focal points to receive MARS notifications directly from UNEP’s IMEO. Alternatively, the notification is shared with the UNEP Permanent Representative. Facility operators that are members of OGMP 2.0 will also receive notifications directly from UNEP’s IMEO. More information on the notification process is below. 

MARS brings together four critical components to drive transparency and enable emission reductions: ​

1. Detection of large sources of human-caused methane emissions.​
2. Notification of relevant countries and companies about these detected emissions.​
3. Response from notified stakeholders to address the emissions.​
4. Tracking progress of actions taken to reduce emissions and collaboration to prevent future methane

MARS is the first global system that provides actionable and transparent data from satellites, directly enabling governments and companies to credibly reduce their methane emissions and drive progress to limit the rise of global temperatures.

MARS plays a unique role by drawing data from nearly a dozen satellite instruments and providing it in an accessible and actionable form. The system leverages UNEP’s global reach across governments, civil society, and the private sector to put this data in the hands of stakeholders who can use it to drive down methane emissions.​

MARS was announced at the 27th United Nations Climate Change Conference in November 2022 and began its initial pilot phase in January 2023. The pilot phase presented an opportunity for UNEP’s IMEO to engage with partners, countries, and operators to refine MARS processes and procedures before making data public. 

Since December 1^st 2023, MARS is operational and data are made available at: https://methanedata.unep.org 

From COP29 onwards, the IMEO data platform, where MARS notifications can be viewed, will offer increasing levels of detail and functionality

Currently, the focus of MARS is on detection and alert of emissions in the oil and gas sector, with the intention to eventually incorporate additional methane-emitting sectors as detection technologies improve.

Any questions about MARS data or process should be directed to unep-mars@un.org

Qualified remote-sensing experts in UNEP’s IMEO use the existing suite of public Earth Observation satellites to detect emissions, trace them to their source, and quantify them across the globe. 

Data from these satellites is publicly available, though often requires specialized remote sensing expertise to properly interpret. UNEP’s IMEO provides this expertise to the global community to supply actionable data and further the goals of the Global Methane Pledge. 

Below is additional information on the satellites MARS draws data from:

There are some fundamental limitations to using satellites for detecting emissions, tracing them to their sources, and quantifying how much methane is being released into the atmosphere.

First, satellites can only detect methane when sunlight is available and where there are no clouds. This is because satellites detect methane using sunlight reflected from the Earth’s surface. It makes it difficult or impossible for satellites to detect methane emissions in persistently cloudy areas of the globe.

Second, the brightness and topography of the Earth’s surface that reflects sunlight back to the satellite also influences whether a source of methane can be detected. It is difficult for satellites to observe methane over or near water, in densely forested or complex regions (e.g. mountains or cities), and where there is reduced sunlight (e.g. high northern latitudes).

Any satellite also has a Minimum Detection Limit (MDL), which means that it cannot observe methane unless it is present at or above a specific concentration. While satellites are often capable of detecting large emission events, it is also important to address the many smaller sources of methane that in aggregate make up a majority of the world’s methane challenge.

In some cases, satellite limitations prevent detection of methane across certain parts of the globe. For example, because satellites require sunlight reflected from the Earth’s surface to detect methane emissions, persistently cloudy regions or those with reduced sunlight present barriers to detection of emissions.

See the two previous questions and answers above for additional detail on satellite capabilities.

Additionally, because the project’s focus has been on methane emissions from oil and gas, the current distribution of detected events could reasonably be expected to be seen in oil and gas producing regions and not elsewhere. As MARS explores incorporating other sectors, the distribution of detections by countries may shift.

The following data is made publicly available after 30 calendar days post-detection: 

• All IMEO-gathered satellite data and related metadata (e.g. visual data), including non-notified data.
• If feedback was received to the notified plume from either the operator or the government.

In the future versions of the platform, additional information are expected to be available to the public, including :

• A summary of operator and/or government response(s) to the notification process.
• A summary description of mitigation efforts and/or plans.
• Any past or future MARS detections linked to the event location.

Data is made available after 30 calendar days post-detection period for a number of reasons:

• To allow experts time to ensure proper data quality and assurance so that the data remains reliable and actionable.
• To ensure there is time to engage governments and companies on emissions events and identify resources that can support efforts to mitigate them.

MARS combines the capabilities of satellites with a broad view of emissions across a large area with high-resolution satellites that can monitor methane emissions down to a small area on the ground. This enables a “tip-and-cue” approach.

1) Regions of Interest (ROIs) are determined through:

• Averaging observations from lower-resolution satellites like TROPOMI, GOSAT/GOSAT-2, or in the future MethaneSAT, which cover much of the globe on a daily basis to identify “hotspots.” These are regions of higher methane concentrations that indicate emissions from one or more significant sources.
• Analysis of individual methane plumes detected from a non-targeted, continuously observing satellite instrument such as TROPOMI, Sentinel-2, Landsat, or EMIT.

2) Once a ROI is determined, UNEP IMEO’s actions will include one or more of the following:

• Search available high-resolution satellite records for recent emissions from the ROI.
• Search available high-resolution satellite records for indication of long-term emissions from the ROI.
• Target high-resolution satellites, such as PRISMA and EnMAP, to look at the ROI to find current emissions.

3) After a ROI has been investigated once, MARS utilizes deep learning models to monitor data from continuously observing high-resolution satellites for future emissions from the region.

4) Notifications are sent to governments and companies once high-resolution satellites can locate emissions at the facility-level. These notifications may be “batched,” meaning they may contain emissions from one or more facilities over a recent time period.

More information on the satellite methodology can be found here.

Once UNEP’s IMEO has identified methane emissions from an oil and gas facility using high-resolution satellite data, responsible stakeholders (e.g., government officials, facility operators) can be promptly notified of this emission. If multiple emissions are detected in the same country at the same time, they may be “batched” together into a single notification.

Through MARS, notifications of detected emissions events are shared directly with governments and, if possible, facility operators who are members of UNEP’s Oil and Gas Methane Partnership 2.0 (OGMP 2.0). 

While UNEP’s IMEO urges rapid action to mitigate observed emissions, the discretion to act and timeliness of a response related to a MARS notification rests entirely with the relevant government and/or operator.

1. Notification procedure to governments, with two options:

Option 1 – Dedicated MARS Focal Point

• If a MARS focal point has been nominated, the notification is sent to them, and the government’s UNEP Permanent Representative is copied in the communication (if appointed).

Option 2 – No Dedicated MARS Focal Point:

• If a government-nominated focal point for MARS is not designated, the notification is sent to the government’s UNEP Permanent Representative (if appointed). 

2. Notification procedure for facility operators:

If UNEP’s IMEO successfully identifies an emitting facility linked to an operator who is a member of UNEP’s OGMP 2.0, the notification is additionally extended to that operator, after communicating with the government. If no such link is found, UNEP’s IMEO will request the government’s assistance in notifying the facility operator.

• A MARS notification is shared via email to the government and to the operator, as relevant and as indicated above. The notification contains the following information:
  • Location of the event (exact latitude and longitude)
  • Time of detection, the satellite(s) used
  • Potential operator of facility involved
  • Potential source of the event
  • Potential magnitude of the event (emissions rate and associated uncertainty)
  • Any subsequent detections that have been made, including any previous detections determined through analysis of archived data.
  • Satellites used for the detection and corresponding images of the plume.

UNEP’s IMEO encourages governments to acknowledge receipt of the MARS notification as soon as possible. If the notification was not shared directly with an OGMP 2.0 member operator, the government will be encouraged to confirm the operator and transmit the notification to the relevant operator. 

From there, the government is encouraged to communicate with UNEP’s IMEO any findings from the operator, and to work with UNEP’s IMEO and partners to take action on the emissions event as soon as possible.

UNEP’s IMEO will keep the government informed of any communications with operators as well as the final outcomes of any mitigation processes put in place. Further, UNEP’s IMEO will share with the government any additional satellite data localized to the notified site(s) that becomes available in the 30 calendar days post detection.

UNEP’s IMEO requests that operators first acknowledge receipt of a MARS notification as soon as possible and provide initial information known about the emissions event in question (e.g., facility type, ongoing operation potentially responsible for observed emissions, etc.).

After providing this initial feedback, the operator is requested to provide more detailed final feedback within 30 calendar days post detection via a form provided by UNEP’s IMEO, including mitigation plans. Further, UNEP’s IMEO will share with the operator any additional satellite data localized to the notified site(s) that becomes available within 30 calendar days post detection. 

At any time during the process, operators are encouraged to communicate with UNEP’s IMEO regarding the notification. UNEP’s IMEO and its partners stand ready to aid with mitigation efforts as requested.  

If a mitigation action is undertaken and information is provided on this action to UNEP’s IMEO, further analysis of satellite data through MARS can verify the success of the mitigation.

Not necessarily. Methane emissions are also detected from satellites that do not have a high enough resolution to identify the facility responsible. For example, plumes from ESA’s Sentinel 5-P TROPOMI instrument, which has a coarse pixel-size, cannot always be attributable to the facility-scale. MARS cannot notify individual operators of TROPOMI-detected plumes unless also able to co-locate a detection with a high-resolution point source imager (e.g., PRISMA, Sentinel-2; see Table) or receives other data that confirms the facility-level source of an emissions event. Consequently, most TROPOMI-detected plumes cannot be notified. 

Most MARS notifications are based on detections from high-resolution point source imagers. During the MARS pilot in 2023, notifications were only sent if a contact was established in the government where an emission was detected. Following the full launch of MARS in early 2024, all notifications are now sent to designated focal points and/or the UNEP Permanent Representative. 

Any questions about MARS data or process should be directed to unep-mars@un.org