To download historical data for the Deposit index on Aave scan, you can follow these steps:

Go to the Aave Scan website: https://aavescan.com/

1. Click on the "Deposit" tab at the top of the page.

2. Scroll down to the chart and click on the "Export Data" button located just below it.

3. A pop-up window will appear where you can select the time range for the historical data you want to download.

4. Select the start and end date for the historical data you want to download, and choose the data format (CSV or JSON).

5. Click the "Export" button to start the download of the historical data.

Once the download is complete, you can open the file using a spreadsheet program or data analysis tool to analyze the data.